How can you reboot an anthology series?
Because "reboot" does not only mean "create a new version of an existing continuity." That's the usage that's become prevalent in fandom in recent years, largely under the influence of the Battlestar Galactica
reboot, but it's not actually defined that narrowly in the industry. In industry terms, a reboot is any attempt to reinvent or revitalize a dormant franchise, to update it in a way that will make it relevant and engaging to a present-day audience and thereby make it profitable again. And it doesn't matter to them whether they do that by creating a new, separate continuity or just revamping the old one. It's not about continuity to them. What the studios and networks are trying to "reboot" is the revenue stream that the franchise can bring them.
After all, the term "reboot" originally comes from computing and means to restart a process that was shut down. Strictly speaking, it refers to restarting the same
process, not replacing it with a different one, so the case could be made that what fandom perceives as the standard definition of "reboot" is actually a complete misuse of the word. Something like "recoding" or "upgrading" might be a better computing analogy for that.
So there's no point in being nitpicky about what constitutes a reboot and what doesn't. It's just a rough, figurative analogy in any case. Heck, even its "literal" computer usage is itself based on a fanciful slang metaphor (to pull oneself up by one's boostraps).