Lots of people are running RISC-V, so this definitely isn't true any more. It was true at a time, but not any longer.
OTOH, I run the only 1U VAX in the world (http://vlc.zia.io), and if anyone else were running anything similar, I'd have heard about it. Still waiting :)
The VAXstation itself doesn't take much power and therefore doesn't generate too much heat. The power supply moves a small amount of air by virtue of its fans, but not much.
It was tested and runs fine in a room at ambient temperature (72º), fully closed, with no external airflow. Because of this, it should never have issues where it's colocated because the datacenter has positive pressure cooling.
OTOH, I run the only 1U VAX in the world (http://vlc.zia.io), and if anyone else were running anything similar, I'd have heard about it. Still waiting :)