Yes .. There is the math ... and then there's the hand being played, which includes the Board and player 'information' received during play. There are plenty of little influences to consider ...
Which 2 are in your holding? Which 2 are on the Board?
These Boards are WAY different ... You hold 9
T
A
J
4
v A
6
7
Or
A
5
4
v A
8
3
Against which Boards is your flush draw more likely to be good?
How do you view betting players and/or calling players during these hands?
How do you view players who double check their cards and sigh muck when facing a pot-sized bet?
Did the PF raiser fold out and you are now facing a limp/caller?
How do you view these Boards when holding a naked A or K of
?
These are factors that may allow you adjust 'available' outs or opponents holdings .. not 'well some might be in the muck'.
Have you heard of this game called PLO? There are more cards in the Muck than the Stub once the Flop comes out .. .can't let that affect your 'true math'. GL