1964 Cast iron Shower drain curiosity

I am rebuilding a shower stall and found what I think is unusual. This one is between two floors of a condo complex. The ceilings are dropped to 7 ft elevation in the central utility ares of each condo, so there's almost 2 ft under the floor.the trap and stand pipe are are 2-7/8 (2-1/2" NPS). this setup has an older style iron shower drain assembly with 2" NPS female thread bottom connection.
It appears to me that the 2" pipe that is threaded into the assembly simply has been stuck down into the 2-1/2 stand-pipe. There is no bell opening (for oakum/lead) at the top of the stand-pipe. The stand-pipe is maybe 16" tall. The 2" tail that is inserted goes down below the water level in the trap.
The 2" and the drain assembly are very obviously not centered in one another, but the connection seems to be quite firm.
Has anyone seen this as standard practice? It seems that should the trap become clogged, spillage out the top would occur.

Thanks very much - this one puzzles me.