Those are the sort of really compact ones I've seen on some other cruiser's boats. They must be popular. However, unless you really cannot fit anything else in, I would think it is a mistake to have a bike with such tiny wheels--you'll be working very hard for the few miles you'll be able to ride it. It is great for commuters who want to carry the bike on the train and ride on either end of the commute. We see a lot of that here in the San Francisco Bay area.
I note they don't tell you the wheel diameter on the site for the particular bike. When we were searching for a folding bike, we wanted a bike that could really go places. The average distance we've ended up wanting to ride it is usually more than 5 miles. When anchorage hopping in San Diego and moving a car around the metro area for the "next" spot for a bit, it is pretty common that hubby was riding ours 15 to 25 miles.
We read something in a biking magazine about how one shouldn't go too small with the wheels--and I think the mag may have specified that anything smaller than 20" was too small. A bike such as ours has 20" wheels--they're small but not so small that you can't make good time for your effort. We've had our bike since about 2004--purchased it to use with commuting around town (DC at that time) rather than using a full size bike. I note that the updated version of ours is now a 7 speed on the Dahon site. Boardwalk D7 | Dahon Global
Some cruisers do manage to stow a fullsize bike aboard--it will depend on your bike and boat if it is possible. CL member Mate1860 manages to stow away not one but 2 full size bikes under their cockpit while underway in their little Albin Vega (a 27 ft boat) so...food for thought...