This is correct; Galvis entered 2017 with service time of 4 years, 21 days. He'll be eligible for free agency in October 2018.
If the Phillies conclude (as some here evidently have) that J.P. Crawford isn't going to pan out, then they have a problem. Freddy Galvis will be a free agent in 15 months. If they're not going to go with Crawford... what ARE they going to do? Extend Freddy Galvis for several years, and gamble that he will continue to be acceptably productive through age 32 or so? If they don't, he's gone. Outta here.
If, on the other hand, the Phillies conclude that Crawford will eventually be better than Galvis - even if that's in 2019 - then does it not make sense to move Galvis when the potential return is relatively high? E.g., a club acquiring Galvis in July 2017 will offer more than club acquiring Galvis in December 2017; and the December 2017 club will give more than a club trading for him in July 2018. A club signing him as a free agent in December 2018 will give the Phillies nada.
My guess is that they don't think Crawford is quite ready - that they don't really want to promote him this month, but want him to continue to work on things in AAA (and they want to see if, post-injury, he's getting his game back together, or whether the last few weeks is a fluke). But this winter? It seems to me that they really need to decide by this winter - if Crawford is the future, then they need to move Galvis while they can get a return for him. If Crawford is NOT the future, then they need to extend Galvis (or trade for a shortstop). And no, Galvis isn't going to be the "super sub" in the Andres Blanco role any time soon. If the Phils aren't starting him (and don't extend him), he'll be a free agent, and he'll go where the opportunity is.