If there are no holds available for a patron, the message "Too many holds" can be confusing. Couldn't Koha simply say something like "There are no available items that can satisfy this hold." ?
I am not sure if this would be better. If Koha says too many, I know that the reason is in the circulation rules (somewhere it limits the number of holds for the user). If it says 'none of the items' I would assume that I can still place holds on other records and that the issue is item related. I think being as precise as possible should be the goal to allow for easy 'debugging' of circuation rules and to understand what's going on.
All I can say is that it leads to confusion to some libraries using it. I think we could be more accurate. I think having it generalized like this is over simplification.
I am with you on more accurate vs. it being too general.