you nailed it. It is virtue signaling. A theater to display to everyone that you are on the right side of the debate and that you are taking covid seriously.
I would even bet that most people issuing the cleaning guidance know that it is almost useless, but we live in a world in which it is more important for your actions to make you perceived the way you want rather than being effective.
I think they're right for the wrong reasons. It wasn't that it was done to be "on the right side", it was done because it was cheap, visible and allowed everything to continue as it was with as long as we all "just wash our hands". Instead of being a method to control the spread it became "the" method and other far more effective measures (masks, WFH) were ignored.
Months into the pandemic they were deep cleaning public transport in my city several times a day but not mandating masks. The cleaning probably wasn't a waste, but it was by far the less effective option. A year on the opposite is true because it took so long for science/guidance to update and for that to filter through to public policy.
I would even bet that most people issuing the cleaning guidance know that it is almost useless, but we live in a world in which it is more important for your actions to make you perceived the way you want rather than being effective.