Actually yes, there can be very big differences between a 10:30 and 10:40 girl based on their running background. I just used an example of girls who were reasonably close time-wise to each other, but the same can be applied to a 10:30 and 11:00. I had a 10:59 girl two years ago (18:48 5k pr in XC), who opened up in 20:35 for 6k in her first college race on a decent course. Her roommate ran 10:32 in HS and ran 20:55 in that same race. By the end of the year, the 10:32 girl closed the gap a little bit, but that same 10:59 girl is still faster than then 10:32 girl currently.
Both were under trained in HS. Both did 25-30mpw. The difference was that the 10:32 girl did a long run occasionally and some speed work (too much). The other girl didn't do long runs and her only workout were fartleks. No coaches were paying attention to her but I offered her big money anyways because I think her potential needed rewarding and she came from a tough background. Plus I was afraid another coach would get her if we didn't get her in the early signing period.
On paper they are vastly different. But once I got to know more about her and watch her race a few times, I saw she was a competitor and had huge upside--so I banked on it. These girls aren't even as rare as you think and a story like her's comes around once every two years for me. Sometimes I get multiple in the same class. This has been a big post for a simple answer....but it all really depends. In my opinion, there are not big differences between both the 10:30->10:40 types and the 10:30->11:00 types if you know where to look. Most coaches would say in "general" this doesn't ring true, but then again, they just aren't trying hard enough in recruiting in my opinion. If these two girls, who are 30 seconds apart in a 3200m in HS, can be so similar, then there isn't much preventing a 10:30 and 10:40 for being similar or totally not a like. It all depends.