Not hating on open source, just let people use what fits their expectations and needs and stop deterring them with gatekeeping :P
UX = user experience
So for one he's adding an option to fund your instance as well, but also just because it's an app doesn't mean that it also doesn't require money.
Your argument doesn't come off as "so both should be free" but to me more like "oh yeah I'm surprised Lemmy doesn't have an ad option"