Maybe, but despite what a lot of people seem to think, Netflix does have original shows that run for more than just 3 seasons, Stranger Things and Camp Cretaceous are two that come immediately to mind. Personally, I like to think that the writer was just being smart and instead of creating a series that would just wander and meander until it's eventually canceled, he crafted a story with a definite ending. Given the nature of the series' premise, it makes a lot of sense since too many series whose premise is to work to a certain end goal tend to end either on a weak note because the series was dragged on for too long or ends on a cliffhanger before it can be properly ended. By doing a B5 and writing with a set number of seasons in mind you avoid all of that, no matter who airs/streams the show.