Probably due to Serif's reworked V2 code base here. - For the Apple OS RAW engine, you can also see instead, if and how their Apple tools like Photos.app or Preview.app etc. handle your Sony .ARW RAW files then in terms of loading speed.
And since Serif's RAW engine is based on LibRaw, you can also see and compare how other free RAW converters (like RAWTherapee, Darktable, digiKam ... etc.) which are also then based (do rely) on LibRaw, do handle your .ARW RAW files then in terms of loading speed.
