I have noticed that too but where able to negate the effect by switching to BTRFS. Startup times on R4.1 using the default disk partitioning scheme and format are an average of 1.6 seconds longer for me[1]. Starting a backup is another situation showing an extreme performance gain using BTRFS.
@renehoj recently pointed out that the amount of memory allocated to a qube makes a difference in the startup time[2]. Most of my application qubes are consuming between 500-800 MB.
I have so far refrained from enabling testing as I can’t afford to hit a bug in the middle of the work week. The freezes are infrequent enough to no be a major issue but I am also one of those people who hits Ctrl+S all the time almost unconsciously after loosing an entire days work almost 30 years ago.