I wouldn't think Bitcoin has, or can, be trademarked or copyrighted, as it is an open-source protocol/technology where even the creator is unknown?

It's still the name of a specific product/service. The issue is partly trademark/copyright, but also party a matter of neutrality. The Unicode Consortium want to ensure that they're not directly or indirectly endorsing any specific products. If they added a Bitcoin logo, then you'd see every other crypto lining up to get their logos permanently installed on every person's devices, too. Free advertising for life on 99.99% of phones would be hard to pass up.