Why is "Tathāgata" not "One Who Is Thus"?

[Adutiya]

This may add to this discussion:

Is satta a mere verbal gloss on tathāgata?

The Pali commentaries often gloss tathāgata (“realized one”) with satta (“living being”). This happens especially, but not solely, in the context of the tetralemma regarding the survival of the tathāgata after death. Analayo (Comparative Study, vol 1. p 391) gives some examples: In regard to the destiny of a Tathāgata after death, one of the two Saṁyukta-āgama parallels to the Aggivacchagotta-sutta (SĀ2 196 at T II 445a18) speaks of the destiny of the “self of beings” or the “soul of beings”.…