> Or is the performance of those models also worse there?

The context and output limit is heavily shrunk down on github copilot[0]. That's the reason why for example Sonnet 4.5 performs noticeably worse under copilot than in claude code.

[0] https://models.dev/?search=sonnet+4.5

Github Copilot is likely running models at or close to cost, given that Azure serves all those models. I haven't used Copilot in several months so I can't speak to its performance. My perception back then was that its underperformance relative to peers was because Microsoft was relatively late to the agentic coding game.