Steel Defenders are "biological" Constructs?

[JackPhoenix]

Fun fact: the Iron Defender (E:rftlW) is also "biological" in the same way the Steel Defender is.

No, it's not.

Tasha's has been out for quite some time. If it was supposed to be Errata'd, it would have been by now. There are other Constructs and Undead and Oozes that need to do...Stuff. It's different for every creature so I assume it's on purpose. Every creature unless specified needs to eat, drink, sleep and breathe. Even the magical ones.

Again, Constructed Nature trait of various constructs is not a part of a stat block, but of the creature's description, which monsters from class features (and spells) lack completely. There's nothing to errata (even ignoring the WotC's incompetence and inability to fix even more serious issues).