The risk here isn't that your snooping boss feels a bit uncomfortable.
The risk is that your snooping boss now thinks they'd better not send you on that expensive training course or assign you that big, important project where success could get you promoted. And that you'll never get a chance to address their fears, as they want to keep the snooping secret.
"Could" is such a big word. It means nothing, but it is intended to be very valuable. Get that promotion in writing. Otherwise it's a carrot to dangle upon you.
> they'd better not send you on that expensive training course
You know what's worse than training people and then these people leaving? Not training them and then these people staying.
You insist on giving me reasons to stay away from that company.
Get it in writting? When in the history of the mankind it ever happened? Not to anyone I know, and I would never make such promises as well. Promotion depends on a lot of things, and promising something like that in writing is stupid.
And once you're tagged as someone who might be leaving, some employers really may prefer no to invest in you. Why should they? You might leave.
The whole argument of "the risk of training and they staying" depends entirely on how you gauge risk. In this case, if you have positive evidence that they are unhappy, then you know that the risk of leaving higher than staying.
There's a reason that so many people now get prompted by moving "horizontally" between companies, very few companies today properly reward loyalty, if anything most actively incentivize individualism and disloyalty.
There is always "we fired 20% of the people, now their workload is on your shoulders or you will also be fired".
There is always "here is a book titled 'use agile to deliver twice as fast' now the deadline is in 3 months instead of 6 or else".
The only defense against that is having more options.
Wheels gotta move I guess, it's in their nature after all.
What a great reason to encourage employees at the margin to job hop! Better pay, negotiation of those expensive training courses and/or big important projects.
What's the downside here, exactly, to a more fluid labor supply/supplier's market?
Big Tech started with a lot of power in labor due to the knowledge economy, and is losing a lot of their core power. Thus wages will start slipping more and more and converge to general market rate for talent. Reclaim that power!
If you're working for a company that actively monitors this sort of thing, I don't think that management's response will be "let's make our employees; lives better."
Some findings show as low as 3.5%
https://www.bbc.com/future/article/20190513-it-only-takes-35...
Some managers are just a--holes, granted.
You don't give your time to an employer, you trade it, and in our modern society we have a gap in the market power of labor. Only way to get it is to reclaim it.