I worked for a company where I designed hardware products at that rate, although not for as long. Someone in management discovered that each time you release a new product you get a huge sales bump from distributors filling inventory. We already had a crowded and confusing product line, so the distributors eventually started sending the old unsold products back and asking for a refund, and that stopped that release cadence.
It did limit the complexity of products, which could be good or bad, but the products were pipelined, so having one employee designing them in ~300 man-hours per design, spread out over six months or so, was totally doable. This included the whole gambit, from conceiving the design to component selection, schematic, layout, design for manufacturing, test fixtures and procedures to documentation and ad copy.
I do feel like it's quicker with hardware than software, because hardware follows something like the theoretical "waterfall" method that software has never used, so everything is clearly documented. For example, I pulled up the cheapest transistor from a common supplier, and it has five pages of documentation plus an index: https://www.formosams.com/upload/product/Mosfets/FMSBSS138-Q...
Everything is always easy to look up, with consistent formatting from every supplier, and you're never dealing with APIs that don't do what you'd expect them to do. You also don't need to continuously fix older releases, because they worked when you shipped them. On top of that, if a component is commonly used, it'll stick around for a lifetime, even as newer products come out, so you don't need to update your product unless it's worth the cost savings.