[GAMEPLAY] Unflinching rune doesn't grant slow resistance per summoner spell on cooldown

The rune "Unflinching" from Resolve tree should grant 10% slow resistance per summoner spell on cooldown, however it doesn't. As seen from video, Fizz's movement speed gets lowered to 235 from Ocean Dragon's attacks, and once Flash is used it goes up to 250, however once the 10 second duration of Unflinching expires it goes back down to 235 while it should be higher than that.

Steps to reproduce:

1. Use a Summoner Spell
2. Wait 10 seconds
3. Get slowed

Expected result: you're slowed for 10% less Actual result: you're slowed for full amount

It has a 100% reproduction rate.