Why do we have to set both limits on rank when matching?

[Vsotvep]

The main difference between 2014 and now is that we switched to Glicko-2 instead of ELO:

OGS has a new Glicko-2 based rating system! [2017]

tl;dr We’re switching to a Glicko-2 rating system, which should be great for a lot of reasons. All of your past ranked games have been accounted for during this transition. Hello OGS! For the past several years we’ve been using a rating and ranking system based on Elo developed by the European Go Federation. It has served us reasonably well, but there have been some shortcomings when applying that system in an online setting. Most of the shortcomings can be traced back to the fact that the sy…

So the whole discussion is different under this new system (at least on a technical level).