An extension like that is used to get the boat into and out of the water on a less than ideal slope and keep the tow vehicle mostly out of the water. You would not tow to the ramp with it extended. The extension would be used after you get to the ramp.
Having typed all of that, there still is a time when the tongue weight when fully extended would be past what those components could handle if anything but straight line maneuvering is involved. That means you would not extend the tongue until backed in, and then it seems to me that while performing the extension the trailer could continue on into the water without the tongue extension which is still attached to the hitch. Then, if you get to the actual retrieving you have to get to level ground to back the extension into the resting position, assuming the trailer must be chocked. Also there would be substantial stress load on that pipe within the conduit and also that bolt, not sure how all this really works outside of the driveway simulation. If the transition from the ramp to flat land is too abrupt then the extension can high center. So, ok, let's say we get it un-extended and locked in, now we are on the road with components not rated for the use even when not extended. Just compare the size of the square tubing on the frame to the size of the new components that replaced the original tongue.
This method shown in the link below may make more sense, just have a long tow rope attached securely to the tongue before unhooking :wink:
https://www.youtube.com/watch?v=kTYCLGVPzUc
