I've got 64gb of RAM and a GPU and running Big Sur. Before this update, I could work in Premiere all day and not have a memory problem. Since the update, I'll be doing simple editing (not rendering or exporting) and within 20-30 minutes I'm down to 6gb of RAM and getting warnings from the OS that I'm down to fumes.
SUPER frustrating! I have to quit Premiere and restart it multiple times in an hour to regain RAM. I've restarted my computer a handful of times as well.
macOS 10.15.7 (Catalina) MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports) 2.3 GHz Dual-Core Intel Core i5 16 GB 2133 MHz LPDDR3 Intel Iris Plus Graphics 640 1536 MB
To test, I simply started Premiere Pro 15.2. I did not open any project, simply allowed it to sit. Memory usage crept up until all of the RAM / SWAP was used up. OS locked up and crashed in about 30 minutes. I tested different versions of Premiere and the earliest version with this problem is 14.3.1. Version 14.3 works fine.