It's hogwash. 15000 miles on 87 and no issues. 100,000+ on 87 on the last two that recommended 91 and no issues; and I've never heard pinging, preignition or detonation. I push these engines to maximum shiftpoints on a regular basis.
The injectors make noise on cold starts; the noise dissipates as the engine warms. Two weeks back mine sat outside for 3 days at about zero degrees. When I started the engine I thought someone had swapped a diesel under the hood. Five minutes of driving and all was quiet.
The injector noise cannot be mistaken for pinging or detonation, except by neophytes. You won't find a gasoline, internal combustion engine pinging at idle unless it was designed to do so, such as the single cylinder, adjustable compression engine used to test gasoline for octane rating.