It was more than that. It tried to influence project priorities by characterizing the impact. The response stated that another way to influence priorities is to pay money. Nobody was being unreasonable. The follow-up email demonstrated low EQ.
I think it's simply a cultural difference, and the message was interpreted by the developer as "give me a date that is close to now to satisfy me" which may or may not be accurate depending on FrugalGuy's intent. But also, the idea that the devs might not care to set and be held to a date seems to be lost on the asker. They probably have not considered that this relationship is not a vendor relationship and asking for something like a date commitment is "out of bounds" for the relationship between them and the OS developers.
Lack of understanding and empathy on both sides for something that probably could have been turned into a fruitful relationship if it had been handled differently (not that it couldn't still, but that certainly doesn't seem like the direction things are going).