It's a very strange locution to frame the last kid on the bus as "do you offer the team an advantage." Where I live 7 run and 5 score. 1-5 get you a team score, advantage regardless whether they suck. If they are 6 or 7 that day, that finish is unpredictable week to week, and that week they don't score and so what if they are 17 min or 25 min. If they are 8 they don't make the bus.
Even if this was like D3 or open entry and you suit up 25, come off it, for true "advantage" purposes it's really only the ones that score or could do so. After that it's developmental, or getting someone a race, or having fun. If guy 24 is not probably scoring why is guy 25 a bridge too far? You're getting arbitrary. And before you go pretending, you are not setting any team "standard" for the fast 5 by how you cut #26. Unless there is a finite resources problem, bus full, too many to run a functional practice, you are just "performing" how "serious" you think this is. Basically asking our license to be a jerk to some kid who showed up and did the work and who you factually have the room for.
Last point but in my experience teams have attrition for various reasons and you're better off keeping bodies and limiting game performance by dress roster than turning away. My college soccer team would cut to 25. But only 18 would travel. And then you'd play some other team with 30 and see where the numbers game was about budgets or artificial notions and not completely necessary. And then people would get hurt and it'd be like, yeah, we could use 26 and 27 about now. One year where we had some flaky frosh and a rash of injuries we're traveling to a game with i think it was 16-17 dressed. I'm like, why don't we undo those cuts.
I see it as arbitrary and performative, trying to send a message that you have to work hard in situations when we already do. My personal experience in college I thought cut 26 was a better player than made 25 and told the coach so when asked. He kept 25. 25 broke my leg kicking me in a captain's practice post-season -- a starter. My HS XC got booted from running that team after I left because of a hazing scandal where a slow runner got hurt they were so rough. To me hazing sometimes happens when you glorify the faster and the upperclass and place the noobs in a weaker situation and maybe browbeat them. Sorry but to me what you're proposing reads as bullying and doesn't actually push the fast kids to be any faster. It just licenses you and them to act snooty. Why don't you worry about yourselves and getting your race time down another 15 secs? Worrying about kid 26 is a fake distraction.