Not sure if I am missing something here, but I play ...c6 against the Classical in the Pirc, 4...c6/5...b5 or 5...Nbd7 against 4. Be3.
So 1. e4 d6 2. d4 Nf6 3. Nc3 g6 4. Nf3 is basically a Classical move order. Then 4...Bg7 is basically forced because 4...c6 trying to get the Classical via this move order I think runs into e5 advances when Black might be tricked and fall behind in development.
So 4...Bg7:
This should go into Classical. But then what if White instead tries a 150 Attack setup now, having delayed Be3:
5. Be3 c6 (to transpose to the Be3 lines, incase White wants Classical also ...c6 transposes to the ...c6 Classical), but then now 6. Qd2:
Now I am not sure if I have been tricked or something, because Black moved ...Bg7 in the 150 where I do not do against the Be3 move order--I usually develop ...c6/....Nbd7/...Qc7/...b5 or ....e5 first. Now if 6...0-0 this is a mix of the ...c6 and the ...0-0 system against the 150 Attack where neither complements the other, and White can try Bh6 since it does not lose a tempo if Black left the bishop on f8.
If I continue with my queenside setup I think that White can try this e5 which causes some awkward problems:
Note that 4. Be3 c6 5. Qd2 b5 with this move order, transposing to the 150 with 6. Nf3 fails immediately to 6...b4 as the e4-pawn hangs:
and notice also that my bishop is not moved, still on f8, plus White cannot develop that g1-knight yet.
So did I get tricked in the move order, and how to deal with this 150 move order if I play 4. Be3 c6, and 4. Nf3 Bg7 5. Be2 0-0 6. 0-0 c6 in the Classical?