As to what kinds of throttling this machine have, I wrote this post some time ago:

https://forums.lenovo.com/t5/ThinkPad-P-and-W-Series-Mobile/P53-CPU-power-management-and-cooling-bugs/td-p/4596511

Since writing it, I noticed that at least with current BIOS, the 50W throttling issue seems to not be permanent, so the system does recover from it after some time (not sure exactly after how much time). Yet the reason for it to go into this state is a mystery to me.

man you did a lot of work I must say. One question came to my mind, if in game I see some FPS jumps from say 80 fps to 140 fsp, does this automatically means throttling?

I can afford to take the time to investigate potential problems these machines have because I've sold 3 of them to my clients and assuming responsibility to supply a properly working device. Sadly this is quite unlike how this industry is generally working.

As to your framerates, there is a lot involved in that and I can't answer your question without investigation, and especially since I don't know any details, such as even the game type, what sort of scenes the game involves and whether there is any correlation between the performance drop and the scenes, how your power management preferences are set up etc. Generally, this might be CPU or GPU throttling but then not every thottling means that the device is not working properly. The CPU and the GPU in almost every modern laptop (except for ones with really weak chips) is capable of providing more performance than the cooling system can cope with. This is just a reality of practical laptop engineering. So basically performance in laptops is limited by the cooling system. Moreover, it is limited adaptively in real time, with many layers of firmware and software governing the ultimate performance by slowing down the chip when necessary. Slowing the chip down for any reason, including thermal, is called "throttling". So from this you can see that throttling is a fact of life in all laptops and that is normal. Moreover, "normal" throttling can occur because of other reasons, for example because of preferences set by the user, for example if the user wants to sacrifice performance for less fan noise or longer battery life.

Now there are cases where throttling is not normal, for instance when a buggy software reads out some sensor and decides to slow down the system for not necessarily a good reason, and then doesn't recover from that state. Or when the software that is operating the cooling system is not smart enough to adjust to varying loads in real time. Or when some driver is not optimized for a specific game. There is much more to this.

To sum it up, probably you are experiencing throttling but I can't tell what would be the reason to that - is it thermal? Is it malfunctioning software? Is it your preferences? Is it an issue with your charger? Or is it just the game being too heavy for the hardware or not optimized properly?

Well, it is not a big deal actualy, to have a slight difference in FPS according to the certain places in the game environment, unless it affects performence. Dropping from 140 FPS to 80 FPS is not a problem at all. Another thing is when it drops so significately that it's no longer playable. This is what I'm expreriencing sometimes, and problem is that I can't pinpoint the event what causes this huge drop. As long as I remember and think, the laptop stays still when this happens. (I made a test to hit table or move laptop during gameplay and yes it drops and behaves absolutly the same way though), but again, I'm not hitting it or moving myself like crazy to hit the table while I'm playing).

Investigating farther I've noticed that when this happens, the GPU usage percentage stays high, say 90%, but the both CPU and GPU temperatures are dropping from the working temperatures.

Looks like it was motion sensor indeed.... Thanks to all and especially to ThinkpadIL for helping me out!

I have it turned off in registry and so far no significant FPS drops.

Why it was triggering emergency mode while I was still and just moving my fingers typing something - is a mistery and just target of another thread I think.