Yes that's a good question... most likely some update, either from Microsoft or from Dell. I'm leaning towards a Dell issue, further research today led me to several Dell XPS users with similar complaints (not exactly the same but very similar, with Excel), and that's where I found about this option.

I would think Hardware Acceleration is pretty useless with Excel, so if it keeps working I'll just take it as a good solution for my laptop

On my desktop PC I didn't make any changes, it works fine like it always did.