Good question. It's very different from a coinjoin, as your coins are not joined with anyone to "hide among others". You are simply swapping your coins on lightning for our coins on e.g. liquid (Boltz is always the counterparty in a swap).

You nevertheless have a nice privacy gain with Boltz swaps because the two transactions of a swap are de-linked, stopping anyone tracing the transaction graph. In layman terms: it's pretty hard to figure out that a particular transaction on the chain is related to a Boltz swap. Additionally, if you swap to Liquid, confidential transactions provide increased privacy by hiding amounts. You can learn more about it here: https://help.blockstream.com/hc/en-us/articles/900001390743-How-does-Liquid-keep-my-transaction-data-confidential-

To summarize, boltz swaps and coinjoins are very different in functionality and goals, but we recently started exploring payjoin, which would further increase privacy: https://gist.github.com/DanGould/425bde63ca13da238071a7935bb3ea3f