Mostly, but not entirely.

Most thing you struggle to approach anywhere near 100% efficient, heating is a bit easier in that you can get a lot closer, but you’ll still hit limits before reaching 100%.

Saying inefficiencies are lost as heat is really a lazy simplification, inefficiencies are lost as anything It just turns out that 95% of anything is heat, from entropies perspective.

If all became heat upon striking a surface that would make lighting anything pretty impossible and most would be dark.