Plenty of S30z's have been selling for $100k plus well before Covid. The Japanese market 432 and 240ZG's for example.
But even in North America the earliest cars have been getting 6 figures for a while.
I don't know if this car is 'mint', but it is nice. $160,000 USD.
https://bringatrailer.com/listing/1970-datsun-240z-101/
But different markets of classic cars are doing different things at the moment. The 90s JDM bubble appears to be popping. Just as night follows day, there is still a lot of those cars out there. Unlike S30z's which are quite rare by comparison these days and often require a lot of cash to restore the bodies on.
Which I think will help them maintain values over the 90s stuff in the short term. Longer term the 90s stuff will come back again, but not before everyone goes broke first due to a global recession.