Does this mean that they can access the site for free by blocking qeys.io?
The ideal use case is a web app (e.g. awesome dashboard) you built and is ran on premise on one of your clients' servers. Their dayjob isn't pirating software, so blocking qeys.io probably has not been on their to do list.
But yes, if qeys.io is blocked, no validation takes place.
My server may go down every now and then, I don't want to deny access to the application just because my 5$/month server is too busy at the moment..