Yes, it seems like Volvo for 1992 (compared to my '80) has improved on the plug.

my earlier response to your other post:

My feeling is that it's a barrier to keep insects from nesting inside. I find wasps (solitary mud wasps or so-called mud-daubers, not social hornets and such) like to lay their eggs and then, having provided a paralyzed prey, seal up the holes with mud. This happens around my house (e.g., in the pocket holes I used to build my deck) as well as at the shore on my boats (e.g., coolant passages on an outboard motor), so I'd like to think that Volvo thought of this problem.

On my 1980 240, I found that the drain tube(s) had a sort of loose fibrous plug (kind of like attic insulation, but much less dense) inside.