Rek Sai Bug?

I'm not really sure where to put this since I'm not entirely sure if it should be considered a "bug" or not but "Report A Bug" was the closest match.

As brand new Rek-Sai player I found myself trying to burrow and E quickly, but then noticing that E was on CD.....why? Then I noticed something. Rek-sai's E ability when burrowed (i.e. her Tunnel) apparently has its own separate CD then her E when unburrowed (her Furious Bite). This mean that if I Burrow, Tunnel, AA to Unburrow, then want to escape, I'll glance down and notice that my E is off CD, hit W to Burrow, but now that I'm burrowed my E is not Furious Bite anymore, but Tunnel...which is still on CD....which means I can't use it.

I don't think that other champs that have changing abilities (Nidalee, Jayce, Shyvana) have this problem (but I haven't been able to test this out), as far as I know they are considered the same spells so if Jayce uses his E in hammer stance and then instantly goes to ranged stance his E will still be on CD am I wrong?