Architecture is a competitive industry. If you want a 3d model you can walkthrough it's not the end of the world - even Trimble sketchup pro has a built in walkthrough tool. You can also export most models to something like cinema4d for a video walkthrough. The models you expect to walkthrough to get some idea of light will require new texture work, lighting, and lots of small details that they otherwise have no reason to add. But those all cost time and money they probably had no idea you expected from them.
The thing is that you probably didn't make your expectations clear up front. If you did architects would quote you a price with that included. But theyd also say something like x revisions and then it's $125/hour so you dont waste their time.
It's a pretty reasonable if you have specific non standard expectations. They'll be happy to mark up the value of having someone else do it and charge it to you.