It'd be a bit weird to have the Sonnet numbering ahead of the Opus numbering. The Opus 4.5->4.6 change was a little more incremental (from my perspective at least, I haven't been paying attention to benchmark numbers), so I think the Opus numbering makes sense.

Sonnet numbering has been weirder in the past.

Opus 3.5 was scrapped even though Sonnet 3.5 and Haiku 3.5 were released.

Not to mention Sonnet 3.7 (while Opus was still on version 3)

Shameless source: https://sajarin.com/blog/modeltree/