This isn't domain squatting.
Squatting is a 'bad faith intent to profit from the goodwill of a trademark belonging to someone else'. That's the legal definition. But they had the domain, they put it to active use for a legitimate purpose. It's no longer in active use. But they had no idea that you would want it. There's no bad faith.
There's also a looser definition that squatting has 'the primary goal being to prevent others from buying it, and the secondary goal being, in many cases, to profit from it.' But this loose goal has a problem - you are in stealth mode. Your own goal is to 'prevent others from buying it' until you leave stealth.
Plus, you do know that they aren't willing to sell, which means they aren't trying to make a profit.
Thus, this isn't domain squatting. This is 'someone has a domain that you want, but got to it first.'
You believe that a domain has to 'create value'? That's not a requirement, nor even a moral obligation. People also acquire a domain with the hope of creating a web site, only to find a few years later they never had the time for it. Or they had a company, the company went under, but they have the domain still because of the hope to start again.
Or, you know, some people have a domain name for email purposes, but don't have a web site.