From my experience in the fleet world, FCA (now Stellantis) will absolutely go out of their way to void warranty. I had two Ram trucks burn out their engines a while back, both were getting regular oil changes at roughly 5k miles. However, both were getting oil changes in facilities that did not keep proper records. We were unable to prove the oil had been changed and FCA denied warranty on both trucks. The agency was stuck with 12k in repairs for each vehicle.
This is not my only example of FCA not honoring warranty, but it is most relevant.
I worked for Ford for a lot of years, we never declined warranty without significant evidence of neglect towards maintenance. Like 30k miles without an oil change is the only time I remember warranty declining an engine replacement.
So yes, he should have read his manual and been certain, but if he had gone with another vehicle manufacturer it probably wouldn't have mattered.