Yup, they even speak HPGL.

Originally, people put knife blades into HP plotters, by modifying the pen holders. Then Roland started making heavy-duty plotters purpose-built to run blades, but they spoke the same HPGL as the plotters, for compatibility.

Then everyone and their brother knocked-off the Roland designs, and of course copied the HPGL compatibility. Along the way, some special extensions crept into the dialect, for setting the downforce (the !FS; command) and maybe other stuff.

And for a long, long time, all vinyl cutters were basically the same. You could use any software with any cutter.

Then Cricut came along and hosed it all up.