Town Hall Upgrades

When you get a new town hall level, building time doesn't actually seem to be that long. My town hall 7 to 8 construction takes 8 days, but it feels like each day is quicker. Still, for town hall 10, it's 14 days.
Well, at town hall 8, when you unlock the archer tower 9 and 10 (which I'm excited about) let's say:
When the town hall is under construction, I access archer tower 9, BUT not 10.
So basically, you get the first upgrade unlocked for the town hall. The new stuff (such as the new archer tower you get at TH 8) is still unlocked after construction is finished.