With the little amount of information I have I would think the controller is not to blame and probably (correctly?) thought the steeper descent was a deliberate manoeuvre by the crew for those few seconds until he realised they were descending far too low and tried to call a g/round.
I am more and more convincesd it was
a deliberate manoeuvre by the pilots.
If the controller was confronted before with the "szczur" (rat, scud running)
landings performed by the Russian pilots before, he might have thought that.
Such "szczur" "procedure" (as mentioned by me before) consists of "diving"
under the clouds before inner NDB, keeping level and on course on NDB and trying
to squeeze the a/c in level flight between the ground and cloud base to the RWY.
So the initial "dive" might have been not that alarming for the ATC,
he has seen it before.
But not arresting the dive on time and disappearing from the radar screen was too much for him.
"Szczur" works well in flat terrain. But you have to bear in mind, that EPWA, the home base
of the 101, as well as 80% of Polish territory and airfields are flat as a table.
Analysing the CVR, I am more and more convinced they were trying scud run
to the runway, what they probably did before successfully, but having
a witness, or two in the cabin they couldn't talk it over, brief each other
correspondingly, and also couldn't comment on the scud run as they
performed it.
This would be also an answer to the question about lack of any comments
from PIC in the last 10 seconds.
He couldn't just say in presence of Gen. Blasik to the C/O "Robmiy szczura."
("We do a scud"), and expect the C/O to support him.