But making news for withholding that technology, thereby drawing attention to and sparking discussion about the issue, can affect public sentiment, which in turn affects policy.
There's also supply and demand. Reducing supply of the technology increases its costs.
The past 20 years (along with PATRIOT act and FISA courts) show that we can "discuss" until we're blue in the face and nothing is going to change. This also seems to be remarkably bipartisan, for a change. The only set of actors that can change anything in US congress are corporate donors and PACs, and Microsoft is a donor (through its employees and PACs, don't know about directly).
Reducing the supply of this particular technology is not going to increase its costs, because literally anyone with a recent GPU and some motivation can just download it from GitHub at this point. The most worrisome user of it, the US government and its various three-letter agencies, already have and extensively use this tech. Casinos have been using it for well over a decade to spot people who are "too consistently lucky".
I do buy your point regarding good PR. It's just completely ineffectual wrt its stated goals.
There's also supply and demand. Reducing supply of the technology increases its costs.
Plus, it's good PR for them.