Most expert snooker players keep the cue more or less level while addressing the cue ball - hence more of a piston than a pendulum. But where the backswing is elongated (and this is usually only on the final backswing immediately before the cue is delivered), the butt will tend to lift.
The reason is that for a short cue travel the motion can be kept more or less level by opening up the fingers of the back hand. There is no need to involve the elbow. But if the cue is taken further back, it can only be kept level by dropping the elbow. This results in the scissor stroke Rick referred to.
Few expert snooker players use the scissor stroke (John Higgins, 3-time world champion, being a notable exception). Most prefer to keep the elbow pinned on the backstroke and not worry about the butt of the cue lifting somewhat. This makes sense: Although the resulting cue movement is more complex than a pure piston stroke, the motor action employed by the player is significantly simpler - there is no need to recruit another muscle group (the shoulder) - and is probably therefore less prone to timing errors.
At the other end of the stroke, the elbow is often allowed to drop after impact with the cb, but this seems to be a matter of personal preference even among the top rank of pros.
Good Post & Thank You for posting it.
I agree with almost all of what you said, but I'd like to say a few things.
I never
'recruit' any muscle group. I know we are talking from a different perspective of outside of the actual execution & the English language can be limiting at times, but I hope you understand what I am trying to say. It's sort of like when others say 'dropping the elbow' & that it needs to be 'timed', etc. NO. I never 'drop' my elbow. It drops when ever it does as a result of another cause or more precisely due to an intention of moving the cue in a particular motion, which is straight. It's different looking at it from the outside & talking about it & trying to describe it, but what we say can, to me, often be misleading.
If I want to & focus on the cue moving straight & level for a power stroke & the elbow lowers on the back swing & other muscles come into play, they do so naturally & with no thought or focus on my or our part. IMO we need to & should trust the amazing biomechanics that have been provide to us.
Also, the cue is moving rather fast, especially for the more powerful stroke where the elbow is ALLOWED to drop as a result of 'a cause'. The video that we normally watch is not sufficient to determine whether the elbow starts to drop before, during, or after contact. We can't even really see it in real life. I would say that only the shooter knows when & perhaps some of us do not even know.
As to when the elbow comes into play on the back & forward stroke depends on a number of things. It may not be that one that has a lifting butt does not care about it but there is something that is causing it. I'm sure that if they could keep the butt from lifting they would choose to have it not lift. But our bodies are all different. Sometimes one sacrifices one aspect of 'perfection' in order to maintain what is perceived as a more important aspect. The focus of keeping the cue in contact with their chin given their physical stance & set up may actually dictate that the butt end lifts for a power shot rather than allow the cue to leave the chin.
A European conical taper is rather different than a long pro taper of many of today's pool shafts. Perhaps if they would rehearse that more full, longer piston action, they might put themselves in a slightly different set up to accommodate it while still being in their 'comfort' zone. Or as you say they are just not concerned about it.
The shoulder IMO is part of the stroke whether it is nearly completely out of play or it gets more involved. I'll say this, When I have either not subconsciously chosen the proper place to connect to the cue or perhaps could not for a given table situation & the butt end of my cue rises or rises too much my stroke gets a bit 'out of whack'.
Perhaps there is a point where it becomes a bit of a catch 22 situation or we have just not yet found a conscious solution or we have simply not yet hit enough of those type of shots with out much time in between them for our subconscious to garner enough of a file base from which to choose properly.
Maybe if one spent some time hitting such shots back to back to back while focusing on keeping the butt from lifting the subconscious would find a natural solution.
Anyway, Thanks Again for Your Post & Sorry for saying way more than I had initially intended.
Best 2 You & Yours...& All,
Rick