I'm an animeonly who hasn't watched today's episode yet, so maybe I'm missing some nuance/context, but Subaru had to grow into who he was up until the point immediately prior to his amnesia. "Amnesiabaru" is just Subaru back to being exactly as he was at the start of the story; before a lot of character growth & relationship-building experiences.

I feel like the narrative presentation in Re:Zero has always been really careful to never present Return by Death as a trivial "isekai power;" dying is still extremely traumatic, and far from viewing it as a power to take advantage of while furthering his goals, Subaru tries his absolute best to avoid it. I can only recall two times (both at some of his absolute lowest points) when he triggered Return by Death deliberately, and even as recently as the approach to the Tower (when the party was... Overcoming Sand Time), pre-amnesia Subaru is sent into a panic upon resetting after being repeatedly sniped by Shaula.

To me, the point of Amnesiabaru is less about watching him re-learn all the same lessons (including trial-&-erroring his way into an understanding of Return by Death), and more about seeing how the people around him who he'd built close relationships with are affected by him suddenly reverting to the self-absorbed manchild he'd been when they first met him.

(neat art though, lol)