I have had the same conversation 9 years ago.
Found elevated temps on roof with spray foam.
They told me foam is not a problem.
I rephrased the question:
Would their warranty hold if heat damage occurred due to the foam holding the heat in the roof system.
Answer: It will not be covered because of heat damage.
The roof can be vented below the shingles as well as between the insulation and the underside of the deck.
Every shingle will not react the same based on wind exposure, orientation, albeto, (Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth’s surface. Ice, especially with snow on top of it, has a high albedo: most sunlight hitting the surface bounces back towards space.).
You can not say foam will not effect the shingles.
The attic air (convection) and ability to radiate is suppressed with insulation lowering the heat transfer from the roof system.
No transfer = retained energy.