A quick look at the HTML confirms, all fields and labels seem to be positioned absolute, each. Might be a good workaround for an MVP form builder, dragging on a grid and using absolute positioning is the easiest way to develop a visual form builder I guess... (although I think a tabindex property would have solved the tab issue, and a simple algorithm sorting divs by top / left would have been able to do it automatically, but this is just MVP).
Maybe I'm wrong, maybe nice HTML doesn't matter, maybe they can fix the tab stop problem, maybe responsive forms are not important to most customers. But everything I was taught is wrong in a web form exists in the form that asks me to sign up for a beta to a tool that builds forms without coding.
Maybe this is the way to MVP... maybe that form was built by an intern. Maybe accessibility is not important for a beta (or maybe I'm the only one pressing tab when filling forms) but this just reeks bad web design practice all over it.
*EDIT: Yep, I guess it was, at the bottom it says: "This Website Was Created with Wix Code". Maybe the genius idea was just to build a fixed grid, forget responsiveness, and solve 99% of the problems of a WYSIWYG editor. All in all they built an MVP and I'm just ranting on HN, so perhaps they are onto something...