the SSD Valve chose is rated 3.3v 1A, the SSD in question is rated 3.3v 2.5A
one can presume that a device capable of using 2.5x the wattage in an already ultra-confined area is going to face some heat dissipation issues at the very least
This right here is the core of the matter. When a Valve provides a detailed guide to replacing the SSD if you really want to, I trust the devs when they say we wanted to have higher storage capacities but heat dissipation was the constraining factor.
You want a Samsung PM991a, a Sabrent Rocket SB-2130-1TB, or a Kioxia BG4, to keep the draw as close to 1 amp as possible. Or slay your battery and bake your internals. It's your hardware, do what you want.
one can presume that a device capable of using 2.5x the wattage in an already ultra-confined area is going to face some heat dissipation issues at the very least