7...c5?! was the pet-line of Bulgarian GM Radulov about 30  years ago and I was impressed then how simply Black decides opening problems - he just takes a central pawn and keeps it to win. Closer examination shows that this is a one-game line. The problem is that White has a strong initiative and can vary plans - atacking on the kingside by e5, f4, or regaining the pawn by accumulating striking force against c5-d4.
Perhaps 7...c5 is not very precise, because it gives White the options (beside 8.0-0) of 8.b4, 8.Rc1,e5 etc. So we discuss only 7...Nh6 8.0-0 c5 to which we like 9.Nb3, but there are also 9.Rc1, 9.Bd5 that also should recapture the sacrificed pawn. After 9.Nb3 our analysis follows the game Partos-Miles, 1977 which you mention. The only amazing thing  about this game is the fact that Black won. After all he was struggling in a very bad position nearly to the end!
One last remark - if you find this line disturbing, do not play 3.e4. It leads to much more tangled positions, than the one at issue. The 7...c5 line is relatively easy for White since he gets an obvious initiative, never mind the final result.