Yeah, that was similar to Amiga and the Kickstart concept, initially on floppy, then as a separate ROM module. Going from AmigaOS 1.3 to 2.0 with the applicable Kickstart ROM gave you a whole new UI layer.
Yes. It was a pretty big chunk, too. Floppies were around 880k and base model RAM sizes were 512k to few MB. Having better part of a meg of libraries in ROM really helps fit more stuff in. And it was possible to load RAM patches or shadow things IIRC.
https://www.amigaforever.com/kb/15-127