I don't think that is the case. At least many users, possibly even most users, would not understand the difference between Apple hosting a social network themselves and Apple promoting a thin client that views decentralized content. If you have an Apple Decentralized Social Networks app, and a parent sees their child viewing objectionable content through that app, a bulk of their ire is going to be directed at Apple; they will likely not even know the name of the entity actually hosting the content.
The "we're not actually hosting it so we're not responsible" argument, I don't think it's ever really worked. I don't think it would work in this case. See: torrent websites.
I think the benefit to Apple also goes down. They give up control, and for what gain?
Heck, integrate it into messenger and treat all content like emoji/stickers you must acquire from a controlled source to circulate.
Legally maybe, but it's nevertheless presented under the Apple brand... which means as soon as the first pedos, QAnon cultists, antivaxxers and other undesirable elements take a look, people will reflect that negatively on Apple.
Apple's brand is basically to be "clean and safe" for users. Engaging in the shitshow that is any modern social network would be one of the fastest way to tank their stock price.