is it fair to say that you would get the same benefit from consistently training at 60-70% intensity compared to only training at 80-90% fewer times per week?

The more frequent the work the more you have to lower either volume or intensity. Try out different programs that play with those factors and see what works best for you.

I was running a program like nSuns or PHUL, would it be advised to use an even lower TM as long as it is done consistently?

You can always lower the training max and use other methods of progression besides adding weight to the bar such as increasing reps during PR sets, decreasing rest times, and increasing quality of reps.

If what he's saying is true then it isn't really necessary to push yourself at the gym, but rather- just showing up and doing your thing consistently.

Bear in mind it sounds like he's advocating for sports athletes not to go all-out in the weight room. He doesn't want them to be too fried for their sports work. If you don't have to worry about football practice tomorrow morning, you can probably push your squats a little further.