Wow, but then I assume they need several more prototypes! Even if we consider the first two FC-31 demonstrators 31001 & 31003 equivalent to the J-20 prototypes 2001 & 2002, so that the two real J-35 prototypes 350001 & 350003 are "equal" to the 2011 & 2012 J-20s, the J-20 has with 2013 - 2017 several more!
Well, entering service in 2025 is still four years from first flight of the true J-35 prototype in 2021 (equivalent to J-20 s/n 2011).
J-20 s/n 2011 flew in early 2014, and J-20 first was received to Dingxin in late 2016 and Cangzhou in 2017-2018 which marked their first entry to service.
For J-XY/35, it will obviously have a number of further prototype airframes built between now and 2025, but in terms of timing I think it actually matches up quite reasonably with J-20.
Keep in mind at SAC they probably have built more flying prototype airframes than what we have visually confirmed because it's harder for us to get pictures.
Keeping that in mind, I think the timeline makes a lot of sense.