In my way of thinking - anything that is alive in the tank affects the bioload.
Bacteria, inverts such as our clean up crews, inverts such as our corals with zooxanthellae, worms, pods, algaes and marine plants - would all either have a positive or negative impact on the tank - or both.
The numbers of living creatures including inverts certainly affects the tank conditions.
A 55 gallon tank with 20 hermits and 20 snails vs the same tank with 200 hermits and 200 snails.
The bioload would not be the same - therefore their numbers and biological/biochemical processes would impact one tank differently than the other.
I suppose it depends on each of our own definitions or understanding of what the term "bioload" means to us.
Everything alive affects the bioload in my opinion.