They are not linkable for the public observer as amounts are blinded on Liquid and additionally Taproot Swaps generally made swap transactions indistinguishable from any other regular transaction. BUT we do have the link! Therefore, privacy on Lightning is a bit better as one can't tell with certainty where a Lightning transaction was sent from. That being said, Boltz respects privacy but is NOT a privacy solution or a substitute for e.g. coinjoins.