To Neil:
I've thought about it more, and my main point is this:
When someone is giving advice, especially an instructor/high level player, the vocabulary should be something like this:
"Learn to play all over the cue ball. Center ball, extreme spin, and everything in between. Do not limit yourself to only one type of play. If you master all of the possible hits, you will have more shots at your disposal, and will be able to use the best one for the situation you face at the table"
And, every instructor on here has said that. As far as just high level players, one in particular has said the opposite, and that is to not use center ball axis at all.
Now, you are correct, when one says something like "use center ball as much as possible", that does not explicitly mean that person is recommending to NOT learn all the other hits. However, I feel it does subconsciously imply that, at least to some extent.
I don't know why you would think that. When driving, you are told to stay in the right lane as much as possible. Does that mean you shouldn't learn how to pass someone by using the left lane? Of course it doesn't, so why would you make the coreelation you did?
So IMO, if the standard advice given was the first one, (and the player followed the advice) the player would put equal time into all the hits. If the advice was the second one, the player would put the majority of time into center axis hits, and by extrapolation, he will be that much stronger in his center ball hits, and weaker in his other hits.
Yes, I agree that center ball hits are more predictable because the CB goes in a straight line, with no squirt, and no swerve. But, to play well, we must know all these deviations from a straight line path to amazing precision, and be able to execute these deviations on command.
My 3 cents