That is true but the problem is in the way it stacks with enchantments and haste. Because it reduces speed to 0 before applying the other bonuses, it causes dullness 5 to cancel out any other boost, even 120 haste and EFF 120.
Confirmed.
It's also annoying how hoppers below furnaces take items out of slot 1 first. Why? They should take items out of slot 3 first, followed by 2, and then 1.
Although you are right that fire resistance only counters the damage from the fire itself it also totally negates all fire damage, including blaze's fireballs. I also feel it's more of a glitch due to the very detrimetial experience PvPing with fire aspect weilding oppoents as the whole fight you can't see half your feild of view even though you're not even threatended by the fire itself. Hiding the HUD is a solution but it will prevent you from seeing your lifepoints bar.
And it would look better over-all.
The glitch happens in 13w10a as well.