To be fair, increasing upload speed can be quite complicated. Merely changing the number from 2 to something larger probably won't have any material effect.
Google places many visible and invisible limits on the use of its public API, and may change these limits at times. As end users, we don't know what Insync's overall usage status of Google's API is. I'm wildly speculating here, but maybe they're at risk of exceeding some limits if they increase the speed too much. Maybe they could request a higher quota from Google, but that may depend on their resources and their relation with Google. Meanwhile, there're other features they could implement or improve independently of Google, and that could be why improving speed isn't the first thing on their list.
That said, I do think Insync can improve their communication with customers. Misleading messages and keeping your customers in the dark are sure ways to create frustrations and resentments.