They didn't; there were many emails throughout 2022 discussing "Important changes to your subscription" from the Google Workspace Team stating that unlimited storage plans were going away and that people were being moved to pooled storage across the entire account.

They were moved to a new storage subscription in mid-2022 and while they were over the limits, Google ignored it up to this point.

He says he believed the data would remain read-only. Did the emails make clear that the data was going to be deleted? If Google had already made that decision then they could have sent him the final warning two months ago.

Maybe they did. Maybe they didn't. We just have half of the story.

To download that in seven days would require something like 3gbit/s

I somehow doubt google drive would even support that level of egress.

it happily chugs along at 1gbit for me, that's the max I can test.

I'd be surprised if it doesnt support it. Its google after all. Despite their shitty customer support, their engineers dont mess around