Mngqithi's side clinched a crucial 1-0 win at Kaizer Chiefs' home ground, FNB Stadium to claim consecutive wins over Pitso Mosimane's defending champions.
Striker Peter Shalulile scored the decisive goal in the 23rd minute as Sundowns - moving to 10 points after four matches played - solidified their chances of qualification for the knockout stages.
"You know what makes this win sweeter? It's beating a collaboration," Mngqithi said.
"You remember during the bubble at FNB, we could not use the Chiefs changeroom. I mean, our countrymen could not use the changeroom but this changeroom was open for Al Ahly now against us.
"For me, winning this was sweeter because I felt Chiefs was being spiteful by allowing Al Ahly against us. I mean, we could have easily taken Al Ahly to the changeroom that has got a ramp on the other side, that long distance.
"It's our home match but it's not our home match when they (Al Ahly) have got a changeroom of the home team. So, that for me was very spiteful because we had almost the same scenario last season but we don't talk about these things because we respect and we are patriotic."
Mngqithi added that the win meant even more as it was achieved despite a "collaboration" between their two rivals.
"Wydad wanted to train at our facility when they were coming to play Chiefs last year but we didn't allow Wydad to train at our facility because that would have meant we are forming an alliance with people from outside," Mngqithi added.
"So, for me, more than beating Al Ahly, I think this is just a good lesson on patriotism"