I actually think this is very well thought out. It maintains the element of exploration during questing instead of just getting attuned asap then fly to complete the quests. For that reason I've been doing quests as they come, instead of going straight for the currents so that I can do the side quests later with a flying mount.
If you only ever level 1 job, sure, you're right.
If you ever start leveling your second job, you will be back there and you will appreciate the flying mount. It's a reward as well as a QoL improvement for your other jobs, not for your first job.
This bug exists for people who are used to "jump" the whistle motion, i.e. you time the space bar to start flying taking into account the network delay, so that you don't wait for the mount to appear. Two ways to mitigate it:
1. Don't jump the whistle motion, let it finish and let the mount appear before you take off.
2. Even if you jump the motion, the speed is corrected the moment you stop and move again. So a quick release-then-press on the movement key will correct its speed.