BU doesn't implement a hard fork but rather potentially infinite hard forks, depending on two user controlled parameters. If the AD parameter is low (the default), then it will just be a long orphan chain, with effectively miner selected block size, but in kind of a gross way (for miners to limit block size they need to orphan other miners' blocks... but they might all have different settings, so it's a risky deal). You also don't know when a chain fork will happen. To avoid this, all users are supposed to coordinate their 'EB' parameter via some side channel, like Reddit. In my opinion this is very error prone, and maintaining consensus is the job of the software, not the user. Earlier hard fork proposals like BIP-100, BIP-101, etc which had BIP9 style voting, or even just a flag day that activate on a certain height, are far safer.
It also doesn't help that BU forked from an old version of Bitcoin Core, which means it's missing some new features and is slower.
It also doesn't help that BU forked from an old version of Bitcoin Core, which means it's missing some new features and is slower.