It may have taken more than 2 years to fix this, but The Sims Team finally did it! The Sims 4’s latest update removes the restriction in Granite Falls which let you place down Rental Lots only.
Thanks to the new update, you can now place other lot types in Granite Falls (residental lots not included of course):
The lots you place cannot be accessed until your Sims pay for their vacation to one of the rental lots in Granite Falls. After that, you’re free to visit any lot in Granite Falls!
Meditating in a Spa surrounded by lively sounds of the nature sounds like a perfect vacation.