You all probably already know but i just want to confirm and maybe there is a work arround.
Tower instructions when approaching Paro Airport (VQPR) are a bit confusing. A flight altitude of 20,000 feet is required for a very long time. In the landing videos, however, the Drukair pilots fly at the minimum altitude of 13,800 feet, as shown in the following image. I ignored the tower instructions and landed perfectly.
In Kolkata there was confusion just before take-off when the tower first wanted me to wait for a plane to take off and then cross the runway. Suddenly I got permission to cross. But when I saw the other machine start, I stopped. 10 seconds later the tower instructed me to wait.
I often get strange instructions from the tower, especially about the flight altitude. It has also happened that I was given a flight altitude that would inevitably have resulted in a crash in the mountains.
If you are interested in the situation on site see the following approach map (refers to Paro Landing as mentioned above):
https://forums.flightsimulator.com/uploads/default/original/4X/6/9/5/6952695498e1fa6dcc0cdfbed1110a69a34fb79c.jpeg
Not really use in sim ATC,
but from your report is clear that speed of in sim objects plays role here, logically 
My thoughts are with Kalkata situation.
Guess you are right. Following the instruction would have led in an accident. Too bad if ATC is not good enough since the simulations itself is great.
Situation can be like this,
you and AI aircarfts are both at h/p of active runway. Interesting is that AI use looks like other runway than you selected or you taxi to parking? If AI still stay at h/p or just start moving, sim has some data and you can take cross rwy permission looks like but your report doesn’t say if AI aircarft has permission to t/o anyway. Why you didn’t select same runway if you’re taxi for t/o? Then maybe TC can do mistakes because if you’re use same runway then this problem probably not existed My opinion only…
I was taxi to rwy behind this resp. i was crossing it when the ai aircraft wanted to start. I was starting at gate and atc lead me to my rwy. It was not up to me.
Now after some more flights to Paro i must say that atc is mostly useless. e.g. it demands a flight level of 9400 feet although the mountains are 13000 feet high at top. Its mandatory to fly at least at flight level of 12800 feet.
This can’t be problem in case of arrival track to final approach goes through some valleys. Logical? You need be familiar with ‘route’ here.