I believe it’s more of a rigidity concern (hobby machine Achilles)
The unbalanced nature of the tool spinning at RPM does not grant much in terms of wiggle room
Some guys are actually hesitant to use it depending on the size on standard knee mills (Bridgeport)
However, I have seen someone mention they have used it on a modded hobby machine. I would categorize it as a more advanced skill practice (wouldn’t recommend to a novice). If one was inclined to try - I would stay below 1.00" diameter swing.
Not so much rigidity as speed - 10k RPM is SCREAMING fast for something this size. These are usually run at a couple hundred rpm. It’ll probably run pretty smooth at 10k rpm, but it’s going to be really hard on the router bearings (out of balance), if it doesn’t bend something or throw it out of alignment, it’s likely to throw the tool out of the holder.
Good to know all that information. I figured it was more a balance thing with it hurting the router or the fly cutter. So if I get a VFD spindle, I’ll give it a try, otherwise I’ll stick to surfacing bits for routers.