Being ona waiting list is not a waste of resources.
My ds is 23 months and behind, developmentally. He is on the waiting list for SALT. he has been on the list for 5 months already, with no sign of the parent empowerment workshop looming anytime soon. I need to jump through this hoop to access the next level of help for ds (such is the game of waiting lists).
If, miraculously, by the time the hopeless workshop rolls around, ds no longer needs help, I will take myself off the list, thus freeing the place for someone else. If he does still need help, I will attend, and ds can go on the next list.
By the time we even get close to 'proper' intervention, it will have been at least 18 months, I reckon. Again, if he doesn't need the help, we don't go - no waste of resources. If he does, the. We might still squeeze some help in before he starts school.
There is no benefit to waiting and seeing. There is potential benefit from being on waiting lists, and no waste of resources as no one goes to therapy/intervention of it isn't actually needed.