The issue of not all deaths being properly recorded in stats is a relevant issue and I believe it is not a feature request. Whilst there are feature requests around potentially PVP related deaths; death by lava, falling out of the world, suffocation, are all valid deaths that should be recorded but are not.

I believe issue MC-79379 should be reopened as an actual bug and not pushed aside as a feature request.

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updated for additional context

creeper (4) + pillager (4) + drowned (1) + witch (2) + zombie (1) + spider (1) + llama (1) + skeleton (6) = 20
Deaths recorded: 25

So 5 are unrecorded.