I doubt he explained anything proprietary as being "closed". He spends considerable time correcting people when they summarize his views and use that term because (as he also explains) that's a reference to open source, a group founded over a decade after the free software movement which ostensibly promotes a development methodology purpose-built to remove the ethical underpinning of free software. See https://www.gnu.org/philosophy/words-to-avoid.html#Closed for more on this. In practice, open source philosophy is disposed of in the face of powerful, reliable proprietary software ("How can I get a copy [of that proprietary program]?") and that's why proprietary software businesses like open source and don't care to discuss anything in terms of software freedom. But software freedom is far better for computer users in cases where the two philosophies conflict or diverge. See the section named "Different Values Can Lead to Similar Conclusions…but Not Always" of https://www.gnu.org/philosophy/open-source-misses-the-point.... for how this plays out in practice.

As to using someone else's tracker (tracking is what those devices do most of the time, so why not acknowledge that's what they chiefly are by calling them by their rightful name?): this is right in line with understanding that software freedom concerns control of one's own computer. Remote services (such as /., Hacker News, Google mail, and more) might run on nonfree software. That's a bad choice for the computer owner (all computer owners deserve software freedom) but it doesn't say much about use of the service because service users don't have a say about someone else's computer. By the same token, those that choose to own and keep trackers on their person have already divulged the location of the tracker (and thus themselves), and that choice was never Stallman's to make. So the choice for Stallman (or someone using someone else's tracker) comes down to making the call or not.