Yes I probably imagined so. For me, as you said, I had thought that the additional 500 baht service fee for the regular service option could have been worth it, just for the peace of mind ahead of a trip to the immigration office.
That being said, just to update, I had written a complaint to VFS regarding my experience and lo and behold, I received a response stating that contrary to what they advertise, a customer's only service choice is the "super urgent' (5000 baht) i.e. next-day service option. Once selected, appointment slots will magically appear to a customer.
So this means that their 'regular' 7 days (500 baht) and 'express' 3 days (1500 baht) service options are pretty much, nothing more than a sham. Why am I even surprised.