Inconsistent rails on pool tables are by design?
If you are asking if someone designs them to be inconsistent on purpose, I would say no. Unless there is some strange conspiracy that I'm unaware of lol.
or
Have Pool Table cushions always been inconsistent and we learned how to adapt as part of the game?
The pool table cushions themselves have not always been inconsistent, but they are so frequently redesigned and reformulated by so many companies (or installed badly) that players are always having to adjust from table to table, from year to year, and decade to decade.
And strangely enough, cushions are to a certain extent "perishable", which can change rubber consistency over a somewhat short period of time in a less than perfect environment. This ads yet another possible inconsistency that players must account for.
Has 3C always had consistent cushions compared to pool tables?
Even back in the day?
3C cushion consistency is not unlike the pool cushion scenario, except that the healthier construction of carom tables helps them to perform more accurately than the average pool table.
A 3C table with pool cushions would be unpredictable and unplayable, correct?
Due to the heavier larger balls, yeah pretty much lol.
Would a pool table with 3C cushions be playable but too predictable to be enjoyed?
Playable ? hmmmm sorta. But I doubt you'd enjoy it. Predictable? Well, once you got used to it, yeah lol
No wonder Pool is so difficult to play!