PowerCON TRUE1 connectors are rated to make/break under load, the original PowerCON 20A/32A are not, and neither are speakON. The problem with using speakON for power is that it would be very easy in their intended environment to get power connections mixed up with speaker connections*. That said, I've seen speakON connectors used for low voltage power even on equipment designed for the entertainment industry (EG, some of Pathway's switches use speakON for 48V POE Supply), so in a limited situation where you can prevent mixups through careful oversight, there's really no issue with it. So unless your steppers are moving around giant speakers that ALSO use speakON connectors that may get mixed up you really have nothing to worry about.
* Before speakON came out, most high-power speaker connections in the entertainment industry were made with binding posts or maybe banana plugs, neither of which was well-suited to the environment and demands of the industry. I've heard stories of some audio production companies overcoming those issues by fitting their amp racks, speaker cabinets, and cables with NEMA 5-15 connectors (which are the standard 120VAC wall connectors in North America). You can imagine the delightful mishaps THAT invited, especially since, I was told, they tended to use receptacles on the racks and cabs, which meant the cables had male plugs on both ends...