That it works for your sister does not mean it works for everybody. Every situation is different.
And again, 0.92 Mbps is not a lot. You can read in his posts that the game works untill a spike in network activity (going through portals) takes place.
And I know what you probably going to say “But yeah, that is DOWNLOAD bandwidth”, but that is just not how it works.
With downloading things you use upload bandwidth as well, and depending on his situation (ISP, hardware, router settings, PC settings, game settings, network card specifications+buffer settings, etc) he can do some things to tweak and get a little bit better performance.
Maybe @GreyArt247 could use Windows performance monitor to see where his problem is related to.