You need to read up on transpositions, dude.
Najdorf Main Line Question

The idea behind not playing 6. ... e5 is that the d5 square becomes especially weak with the f6 Knight pinned, and White still being able to play Bc4.

you can leave the pawn on e7, and play Nbd7, and possibly play e5 in one go later, but its not necessarily bad to slow-step it. e6 makes playing d5 sooner easier sometimes.

6...Nbd7 intending in some lines ...e5 in one go is an interesting and quite topical line. The direct 6...e5 is not good.

I'm not trying to be rude or snide here:
Just start playing 6...e5 in this position whenever you can, and sooner or later your opponents will answer the question for you. OR you can just take it for granted that everyone else knows something you don't and stick with the most popular moves in the Game Explorer here OR you can blindly play the percentages, who knows, maybe 6...e5 will work for you
Why is the continuation 6. ... e6 and not 6. ... e5? Is it not a good idea to drive the knight on d4 away? Thanks in advance!