I bet poor Polish pilot had no idea how exact the ground control sees him, given his equipment. He'd never be interested before, previous years Polish flights there were in normal visibility or, at least, in visibility (not without).
So for him the ground control messages "on the glideslope" must have meant "ground confirms I am doing alright in direction to runway, distance to it by time and height and allowed (correctable in time) deviations left/right".
As a matter of fact may be it was so, until a certain point.
Glideslopes re-built from speech there are already a dozen versions and all quarrel theirs is the best.
Russian blog says by ICAO standards a pilot should not report his height to the ground control, at all. That must have been Capt. Protasiuk's idea.
Moreover, folks doubt in recent practice even in Russian military aerodromes pilots keep to that rule in normal visibility, but, rather, are lax about it, as it is a pre-historic rule. From times when this type of radar equipment was used. (for example, version 7 of this radar is to be found in internet in the Baltics' site - "Museum of aviation" - in the antiquity :o) dpt.Las
That very aerodrome used other things, Russian equivalent of ILS, complementing this radar - when there were miltary planes stationed there and their unit/regiment, etc. But they left. Military left this aerodrome, last summer, were re-located, and took away all their good and useful things with, leaving behind the very minimum. For off-scheduled arrivals, chancy flights, in case they'll need the aerodrome as one-off, and for the use of the aviation factory nearby trying their planes, in construction (as I understood). This isn't a full Russian military aerodrome, this is worse, it is an abandoned version of it. A mini-bikini set. One glidepath direction left, instead of prev. 2 (East and West), from the other landing direction all things exported. 2 Beacons, 1 radar, one control booth looking like a shed honestly, you won't call it "a tower". Good runway though, 2.5 km and even, well/strong done.
The aerodrome rolled out for Poles all it could, built those "gates" of lights before the run-way (and very bright and large, noticed by the Yak, powerful "curve" light reflectors).
I think it's of course comms. There were no girls there! Men aren't talkative, esp. military men on both sides.
When, instead of Good morning glad to see you the Russian control said "conditions for acceptance - none" - why not to develop this further?!
Ask "what do you mean?!" and all.
The Polish crew was quite talkative with Belorussian ground controls en route before. May be if there wasn't his commander neraby, in whose presence he didn't like to lose face - he'd enquire, ask the ground control a couple of things, that flicked his mind.
When the Russian control asks "Have you landed at military aerodrome before?" - why not to ask what do you mean?! And the controller - why not to say what did he mean, by it? That he expects the pilot will be telling him height, or what? They could have discussed the glideslope, when who says what (IMH female O !) and how are they going to do it, in fog, together.
Disaster.