Seems unreasonably slow to me that xterm would take a second to start. My two computers running kernel 6.7 are slow than the machine in the test, both have BTRFS on LUKS.
I tried a cold start of xterm on my older thinkpad with an NVMe drive at ~0.3s.
A cold start on my desktop (also NVMe), 0.08s.
I'm unable to reproduce. I wonder if he might've had a fresh install with some background operations grinding on, or some indexing going on.
Yeah; my somewhat up-to-date thinkbook with NVMe drive cold boots to Cinnamon desktop in under 8 seconds, terminal window opens in the blink of an eye. BTRFS is not without its problems, but they're more along the lines of specific RAID configs not being what you'd wish for; I've never heard a complaint about speed before, and I've never had that problem myself.