That sounds like a conclusive answer... Hmmm... wonder how much an average SSD draws, vs some hotter or cooler running ones. Just finished researching them for a Xmas present for my wife (getting her laptop off a rust drive to a M.2 SSD) and reviews sometimes mention "runs hot" or they have significant heatsinks, vs some that run cool and or are reccomended for laptops for their coolness and improved battery consumption.
Something I wanted to throw in the mix, try to find USB power cables with higher current capability. (not easy to do) Some are made with very tiny gauge wire, for cheapness. You can get a lot of voltage drop, and a heavier load makes matters worse. I've had problems with this even on Pi3's just running music player software. USB3 is better, (available on RPi4?) "charging" type cables should be better, too. Another factor to consider.