I don't think it's bad faith at all. They're up front about what tools the system is built on. It's more about whether it makes the most sense for you to build and host something like this yourself, or pay for what you use on a service that someone else runs for you. There are pros and cons to each, of course, but I think there are a lot of situations where the latter is going to be better.

One example being: if I was building a new product and wanted to add some reporting/exporting features, I would much rather use a service like this. Document conversion is just infrastructure for those features, and so any time I spend setting up my own system for that is potentially wasted time until I can prove that the features are a success.