I assume they would still have the serving code they use now and if they do choose to go back to maintaining it on their own hardware they'll always have that option. It seems they just don't want that anymore.

That will be several years down the line, when everything has bit-rotten to death and nobody in the team remembers how the old setup worked.

That's why they're being encouraged to use cloud run and all the other cloud functionality so a migration back becomes very hard.