It's not a bad choice for everyone .
The tile/word bank option is given as a choice early in a lesson, but later on typing is required.
It's a staged learning curve: simple tiles at the beginning; harder full-sentence typing comes later.
It makes perfect sense to me - and I use it, and like it.
"You have to wait a half an hour" is very common English where I come from. It is a shortened version of "You have to wait one half of an hour" but the word "a" is substituted for "one" (a very common substitution in spoken English) and the word "of" is omitted because it is implied. I believe Duo should accept.
Sort of like the difference between 6 of one, half dozen of the other?
We use different terms for the same concept, and we do that for a reason.
Understanding and accepting new concepts, like this, enhances your depth of learning.
But, if you feel that strongly about it, that is what the REPORT button is for. We are crowd sourcing our learning!
Tener always uses que to mean to have to, not a. I don't think Duo is inconsistent with tener que + infinitive.
Here are a few verbs that need a before a following infinitive: ir a, venir a, ayudar a, invitar a, empezar a, comenzar a, enseñar a, aprender a, y otros.