The way this is worded implies some things that aren’t true.
Just say that Smite bypasses Healing and Death Immunity. It not counting as an attack is irrelevant since both Healing and Death immunity work on many non-attacks. Distort reality for example does not bypass death immunity despite not being an attack.
Defend is the only defensive ability that exclusively guards from attacks and nothing else. If you want to bring up Smite not being an attack then you should do it for this Ability.