The RPi 4 has USB 3 + UAS which is actually quite decent. I use it for Aarch64 development[1]. It boots and runs entirely off the SSD, and the performance is not spectacular but perfectly usable, and being it's a regular SSD it should be at least as reliable as a laptop.
It also has a firmware bug where it cannot boot unless there is an (empty, unused) SD card in the slot, which is annoying!
I've never had the problem either - I started using the RPi4 seriously when it became possible to boot from USB, and it's great. USB boot is working properly in the newest Ubuntu Server and Ubuntu MATE Desktop images as well as the official Raspberry Pi OS.
The Samsung T5 and T7 are frighteningly fast USB-attached portable SSDs - some simple tests of mine had them at around 335MB/s. On paper the T7 should be twice as fast, so it's interesting that they tested so close (the T5 was even a little faster, as high as 350MB/s), but they are both totally good enough.
I boot a RPi 4 via PXE (or rather, the RPi version of PXE, which is decidedly non-standard, meh). No SD card in the slot. No problem. Are you on the latest firmware?
It also has a firmware bug where it cannot boot unless there is an (empty, unused) SD card in the slot, which is annoying!
[1] https://rwmj.wordpress.com/2020/09/24/raspberry-pi-4-running...