The Soviet Union trying to take a chunk of your country is a hilarious piece of fiction taught to Pakistanis. It allows them to take solace after the 1971 humiliation, to pretend that they thwarted and defeated a superpower. It is a broken nation's fairytale to regain some self respect. If the Soviet Union really wanted to invade and annex Pakistan, they would have done so. Nothing short of America fighting for you with all their might, could have prevented that.
The tit-for-tat can be played all day. If the Afghan army tried and failed to take Pashtunistan from Pakistan, then the fitting reply would have been to wage an assault into their territory. Not propping up the most immoral regimes on earth, right next door. Besides, this new take on the matter is...rather new. Until 2001, Pakistanis adored and respected the Taliban, and considered them ideological soulmates. Only when the USA went to war against them, did some Pakistanis reluctantly start disassociating from them. Back in those days, Pakistan supported Taliban because Pakistanis liked the Taliban. It's that simple. It wasn't considered as a means of punishing Afghans for what happened in the 70s. Pakistan wanted strategic depth and leverage, and the best way to get that was by propping up a regime that is bound to be friendly, due to mutual affinity.
Now when the same barbaric ideology has reared its head in Pakistan, suddenly Pakistan is reframing the narrative, and pretending that helping the Taliban was only to punish Afghans and so on.