Yes. Exactly. They won't. This raises the risk that the pick-up won't take place given that they love to phone first and double, triple, check that you are where you say you are.

I love Didi here and I have a China number and place myself near someone young and friendly looking for the inevitable moment that the phone rings.

Arriving at an airport, as a first time Didi user, I would get a taxi rather than try to work things out Chinese-style. IMHO it's doomed to misunderstanding and failure.