I mean they must realise this is a pretty unpopular decision so why not share their justification.
Otherwise it's just an appeal to authority - "Ours not to reason why.."
Sometimes its easier not to share. In a perfect world we'd be more transparent. If its an popular decision, discussion potentially fans the flames of disagreement and ill will. E.g. People take some small point of the rationale and blow it out of proportion for why this is bad etc, why it isn't relevant to them without seeing a bigger picture etc. I think we've all seen this. Sometimes its simpler and more efficient to say less.
I don't agree with this premise. It's quite easy to share "we have data that suggests that this is the case", even if you don't divulge fully what that data is.
A decision where it's clear that some analysis has gone into it (even if you disagree with the outcome) is always going to be more accepted than a decision that seems completely arbitrary / driven by politics.
It seems that developers / ICs are asked to justify everything they do with data - making decisions from the gut is the privilege of the executive.
And there is quite a bit of data on it, most of which is widely shared internally.
Everyone who has made it up the ladder knows this and it's the single aspect that differentiates people who routinely get overlooked for promotions from the individuals who steadily rise through the ranks
A lot of politics gets much harder in remote work, and this is what these people are best at.
It's not productivity, it's politics that is much harder to do when remote working.
They also need to keep an eye on developers and need to feel thigs out, the relationship, their management status known and so forth.
That's very hard to do remotely and they feel their status diminished to that of the "resources" they manage.
That assumption has been thoroughly refuted by Google's reaction to James Damore's internal memo.
But that still assumes the executives making these decisions prioritize employee well-being and work productivity. No amount of correctly collected, analyzed and understood data on WFH productivity will help if the change isn't driven by concerns about productivity. In that case, this data is just irrelevant. I believe this is the concern GP is expressing - that the goals of the management are not well aligned with the goals of the employee (which is obvious), and the well-being of the company (which is plausible).
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[0] - I'm willing to give the benefit of the doubt here to Google, at least in areas where it matters. I'm not usually giving it to a typical company, Internet or otherwise: just because you have data, doesn't mean you have the right data, have analyzed it correctly, or even employ anyone who could analyze it correctly (or employ decision makers who could understand and vet the conclusion of the people doing the analysis). In my experience, these failures are very common.
[1] - I have my doubts where it comes to their product decisions.