Welcome to the forum, tcshome -
Yes, April 25 is Liberation Day, a national holiday, in Italy. As is customary, attractions which are free on national holidays generally don't allow timed-entry reservations or priority entrance. Lines on other days can be avoided simply by purchasing tickets/making advance reservations at attractions which tend to have the longest of them. That can be done via the official ticketing websites for those attractions. Tours not offered by the attractions themselves are best booked directly with the companies which offer them; the better of those have been recommended many, many times by helpful forum contributors.
As Christine said, Get Your Guide, like Viator, is a 3rd party reseller and doesn't operate their own tours. Most of us don't recommend using 3rd parties for booking as you can get caught in a finger-pointing battle between the 3rd party booker and the actual tour company when there's a problem.
That said, advance research before a trip is advised as 4/25 is not the only national holiday or special "free" day in Italy, and museum entries may not be the only sightseeing factor affected. These forums are great resources for questions/research before the trip to help avoid potential missteps so make good use of it before your next adventure? 😉
Aside from that snag with queues, hope you enjoyed lovely, fascinating Florence!