I'm not sure if that stat is supposed to exclude free agents (for example, Zach Baun), but both teams last year had plenty of 3rds and 4ths starting (more than UDFAs). The Chiefs in particular were very loaded. Philly is insanely top heavy with 1's and 2's. I know this is just a 1 year sample size, but no way am I going back to figure out all the years. I believe it probably ends up accurate in some way, but looks to me like it's probably likely that the team is primarily 1sts and 2nds and then it's a wildcard after, with free agents being a major factor.
Eagles:
Milton Williams - 3
Nakobe Dean - 3
Baun - 3
Sweat - 4
Gardner-Johnson - 4
Blankenship - UDFA
Chiefs:
Thuney - 3
Chenal - 3
Hunt - 3
Kelce - 3
Reid - 3
Caliendo (shouldn't be a starter) - (UDFA)
Wharton - (UDFA)