that is all
I am surprised that this statement is still doing the rounds.
"If you want a stronger core, you can’t rely solely on squats and deadlifts to save you. " - Matthieu Hertilus for EliteFTS
"You can't just squat for core work. " - Mike Boyle
"Despite what some coaches are saying, the evidence is clear: You need to train the core for stability, and direct training activates the core more than indirect work." - Alwyn Cosgrove
Heavy squats and deadlifts do product high core muscle activation for sure, but you're only working one movement - extension. Think about all the different ways your core can move, all the different forces that you might need to resist. You need to train them all.