Yes, I have seen this happen on multiple occasions, with both Shturman and Sanitar - the latter being extra surprising because Sanitar is generally both well equipped and proficient in using medical items.
With both bosses, the kill was eventually attributed to a limb hit. The time passed between inflicting the wound and credited kill matched up with the expected time: their better-than-PMC health pool makes even heavy bleeds take longer to become threatening.
I believe I have positively confirmed both bosses and boss followers perishing this way though they still had the medical requisites to stop it in their backpack. We can expect this to become more difficult to pull off as soon as the AI is fixed concerning at least using up what they are carrying.
I have yet to confirm whether this is also possible with other DoT mechanics such as
the poisoned knife found from cultist NPCs (others tried without success so far).
Answered for version
0.12.11 - When trying to confirm whether this still happens in future versions of the game, ensure you really do see/hear the boss die. I suspect certain sources of damage (friendly fire grenades & ricochets) can be ignored when looking whom to attribute a kill to. Thus the post-game summary might imply the boss bled out, when in fact further damage sealed his fate.