I would worry about the kit aspect of the bikes.

You're lucky to merely have to pay some money for your "power kayak".

In my state, to actively discourage the construction of home built boats, if I want to build a 15 foot sailboat, I need to work with the coast guard and state DMV (spoiler, they don't actually work together, the finger pointing is hilarious) to get a hull number assigned, then fight the DOT to get it titled (boats are titled where I live, and its agonizing although it only costs $5) and its quite a fight involving official inspection because most "homemade" boats are people trying to register are Crestliners with the serial numbers filed off, then I can fight the DNR to register myself obtaining a DNR customer number, and then fight the DNR to register the boat, essentially linking my CG hull ID number to my DNR customer ID number for a mere $17/yr, ironically the total cost of all of this for the first year would only be roughly $30 but it takes like 100+ hours of phone calling and meeting people and filling out forms. I pay $35 for a quart of good topside marine paint so the point is not the expense but the bureaucracy agony. All that for basically an inland lake dingy with a sail on it.

That sounds like insanity. My country by comparison is too far at the other end of the scale. Anyone can buy (or make) a boat, with a 200 horse motor, grab a six pack and a tank full of fuel and hit the water and go anywhere, into any harbour, with no training whatsoever.

Many e-bikes are perilously close to motorcycles, with similar power and top speed to a 50cc motor scooter. Brushless motors and lithium batteries can put out a phenomenal amount of power and torque. There's a line between "bicycle with electric assist" and "electric motorcycle with vestigial pedals" - I see an awful lot of the latter these days.

I would hope that they're equipped with disc brakes at a minimum. Wheel rim brakes on a conventional bicycle will slowly wear down the rim, but even when riding regularly, should last for quite a few years. On an e-bike with the faster speeds and greater braking needs, it may shorten the life of the wheels significantly.