It was a different era…
This was the arrangement for most British kayaks for years. The original design featured a long intake hose (ideally fitted with a strum box) that allowed you to pump either your kayak OR to pump out another kayak which was a great feature.
Significant entrapment issues aside, it’s actually quite practical to use, requiring only a bit of torso rotation. Often you would see someone showing off by sculling with one paddle blade resting on one’s shoulder, while operating the pump with the other hand (ala Derek Hutchinson).
The real problem with the location is that it does not permit the bulkhead to be close to the back of the coaming, so it fell out of use with the advent of the day hatch. However this arrangement does allow for some bulky items to be carried just aft of the seat.
The entrapment danger is probably most likely for a layback roll, or possibly if you get flattened to the rear deck in surf. For those who remember this era, the certifying organizations were quite opposed to any lay-back style of roll at the time (calling it poor technique), and a C-to-C roll (coming up from the side) was king. Many sea kayaks of the era (Anas Acuta nothwithstanding) had a relatively high rear deck that made a lay-back roll very difficult, anyway. The growth of Greenland-style technique (with the popularity of the standard Greenland (layback roll) may have helped to change this mindset.
Greg Stamer