Was there a more convenient way to perform the bootstrap? Couldn't it have been in some kind of ROM? It appears to be only a handful of bytes.
Their earlier mainframe cousins often had features to easy "Initial Program Loading". The IBM 1401 had a load button that was hardwired to read a single punchcard (80 6bit words) into memory locations 001 to 080 and jump to it. The CDC6000 had a panel with 144 toggle switches, acting essentially as a 144 bit bootrom. (12, 12bit words) These were expensive mainframe computers, so they could usually afford some budget towards IPL functionality.
But I guess even these cheaper minicomputers were expected to stay on long enough that there was little point spending money on IPL functionality to make cold booting easier.
(Core memory would retain its contents without power, so if you were absolutely sure nothing could possibly have disturbed that initial bootstrap routine since the last time you toggled it in, it might still be there. But a lab minicomputer of that era, probably didn't have any memory protection at all, so that's a pretty big "if".)
Edit: It’s describing a situation where a “Resident Monitor” isn’t built in, but is manually loaded after power up.