A statement from Fairphone once in the other first major thread about the unreleased source code expressed that software development wasn’t done in-house.
So as it looks they were truthfully relying on their development partner to “not be cagey” but reality seems to be different. …how come I am not surprised about that… 
I would not put much believe in this unless the one(s) who have managed to brick their device have very good explanations for anyway being covered by the FP3 warranty regulations according to these clearly written requirements:
Omg, where do have this from? Any serious source or just wishful thinking?
I am afraid consumer rights in general does not cover wishful thinking.
Fairphone initially has advertised the FP2 with “yours to open, yours to keep”. Keeping self repair in mind. Not …yours to tinker with.
They were fair enough to provide these possibilities like an unlocked bootloader [and these left over pogo pins on the back side]. They opened the opportunity to install other OSes beside FPOOS, enable root access. But at ones own risk after all. This was for FP2. The FP3 warranty regulations don’t read much different for me specifically what I have pointed out above.
If you are seriously convinced about your statement I do have to wonder if you maybe by accident got “in touch” with a Fairphone or already have made positive experience with this expectation in the past using other mainstream mobiles so expecting the same from Fairphone. If the latter many of us are surely eager to get to know how positive your experiences were with other manufacturers (repair) service.
Manufacturer regulations and product conditions may change between two steps. What applied to an earlier product does not have to apply to a new product in the very same way.