Definitely not unique - if you've ever seen the code size you can get a Forth interpreter down to, you'd know why it might've been tempting.
There were actually a few of the more obscure systems of that era choosing it - albeit fairly horrific for a beginner to learn compared to BASIC. Some of the Z80-based CP/M ones, for example (the daughterboard in the… um, repurposed?… Torch I had as a child, although what I actually used was the BBC part of it, because come on, BBC BASIC with a built-in 6502 asm!), or the ZX81-style Jupiter Ace.
There were actually a few of the more obscure systems of that era choosing it - albeit fairly horrific for a beginner to learn compared to BASIC. Some of the Z80-based CP/M ones, for example (the daughterboard in the… um, repurposed?… Torch I had as a child, although what I actually used was the BBC part of it, because come on, BBC BASIC with a built-in 6502 asm!), or the ZX81-style Jupiter Ace.