This is IT, I reckon.
CRT have to draw staff from the population as a whole, so there is no reason to expect any given CRT employee to have any greater or deeper knowledge of the canal system an any other random person needing a job.
New recruits probably get sent on a short training course for a day or two explaining the basics i.e. canals were dig manually and are not rivers, why they have locks, and how they are used by boats, runners, walkers and cyclists whose needs must be balanced, and how canals are funded mostly by the guvvermint hence short of money.
Expecting anyone earning £30k working for CRT writing publicity material to know the difference between Rammey Marsh and Romney marsh (or even care particularly) is a bit unrealistic in my opinion. They probably thought they were correcting a spelling error.