Good sleuthing!
However we don't use GeoIP to decide between Instanbul and Frankfurt servers we use ping. It's not ICMP Ping (like ping.exe) but something that's closer to game traffic.
So if you're getting placed on the wrong servers it usually means that your ISP is routing the ping traffic incorrectly. For example if the ping packets go from your computer to Instanbul and then to Frankfurt then it's not surprising that Instanbul's servers have a smaller ping.
This can happen because there are many ways to connect to Riot's ISP (via our PoPs or Points of Presence) and often an ISP will pick one arbitrarily to send traffic to rather than the best one. The fix is usually that the ISP reconfigures their routing (Riot can help them) though sometimes there're other issues too.
Here's a map of the PoPs you can see that if your packets went from your location, to your ISP and then to the wrong PoP your ping would end up pretty bad.
Disclaimer: I'm not a network engineer so I might ha...
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