Although there are a few exceptions out there, I view oil weight experimentation much like tweaking tire pressures or alignment angles. Within reason, personal preference is just that. Personal preference. If a OE said you could only use brand X fuel, and one day you decided to try brand Y knowing full well it was an acceptable substitute, would it be along the same line of thinking? No, it would be considered silly.
OE's have to provide a set of specifications to guarantee that what they're selling will do it's job safely, reliably, and perform within design parameters AT LEAST through the warranty period, although we all know modern vehicles are designed to go far beyond that.
For example: among the multitude of family vehicles I maintain are a 2011 CR-V and a 2018 Accent (same household). The Honda spec's 0W20, the Hyundai 5W20. As many K24's tend to do, the CR-V started burning about 1.5 quarts every 1k miles running 0W20. I told my dad to just buy 5W20 for both, full synthetic as that's what both have been getting since new. No HM, nothing fancy. Just quality oil. Did it have any negative effects on the Honda? Absolutely not, in fact quite the contrary. The oil burning is now down to about 1.5-2 quarts per 5k oil change.
The same can be said for tire pressure. Sure, the OE spec is optimal, however I've been running my tires about 5 pounds high on my Volt and about 3 pounds high on my Jeep and both times it's worked out great. The Volt handles sharper in corners, rides exactly the same, gets better electric range, and the tires have worn absolutely perfect for the last 25k miles. The Jeep is a lot less "floaty" with a few extra pounds, and doesn't lean quite so much on high speed curves.