On the other hand, when Linux was new (I switched to Linux in early 1992), you could install it all on a floppy and boot in a few seconds. Not much difference really. Just way more flexible with a Linux floppy than a DOS one.. I kept a Linux floppy around for doing various stuff with problematic PCs.

It's way more important (or was, at the time) that MS-DOS could run on 8088/8086 and '286, unlike regular Linux.

I'm afraid it would: in 2002 I was involved with the development of a very early wifi AP implementation at Freehosting; this was running uclinux on an ARM7 with a pretty bare kernel and the whole OS fitting in under a megabyte. Booting was already pretty much instantaneous then.

20+ years ago I was able to boot Linux with Busybox on a Pentium 2 in under 5 seconds after the BIOS POST completes.

20 years old? more like 30-35 years old