Guild Wars 2

When i gain swiftness from Signet Of Inspiration and then walk over temporal curtain, i do not gain swiftness from temporal curtain. Is this a bug?

Note:
If i have no swiftness then cast temporal curtain and then signet of inspirations passive activates its stacks, but not when used the other way round.

http://wiki.guildwars2.com/wiki/Temporal_Curtain
“Allies with swiftness are unaffected.”

To be clear, this behavior is “working as intended”. In other words, the devs are too lazy to replace a shoddy bandaid applied in the betas with a real fix for functionality.