Possible I6-related bug when being pushed on an enterable supporter

I suspect that @DavidG might be the person to ask this, but I’m drawing attention to this bug in case anyone else has insights.

When you write this, which has someone push an enterable supporter while you’re on it

Lab is a room. North lab is north of lab. 

The float is an enterable supporter in north lab. The float is pushable between rooms. The player is 
on the float.

Neil is a man in North lab.

Every turn when Neil is in North lab and the float is in north lab: try Neil pushing the float to the 
south.	

Test me with "z".

you get this:

North lab (on the float)
You can see Neil here.

test me
(Testing.)

[1] z
Time passes.

Neil goes south, pushing the float in front, taking you along.

Lab (on the float) (in Neil)
Lab (on the float)
You can see Neil here.

Note that “(on the float) (in Neil)”. The way pushing an object works, if I’ve got this right, is that the object gets temporarily made part of the pusher, the pusher moves in the normal way, and then the object gets put back in the location. It seems as though in this special case, a room heading is being produced before the float gets unglued from Neil. But I’ve been unable to make head or tail of where that’s happening, and I’m not sure if it’s actually something going on in the I6.

For what it’s worth, this does not happen with enterable containers; only supporters.