I can only speak for The Netherlands and a bit for Britain.
For The Netherlands Gouda and Edam are listed, those are two mass produced cheeses with a big export market.
Cheddar is listed a few times on the British Isles, it's very common over there.
Probably the map just lists some common, mass produced cheeses per country. There wouldn't be space for more. The map isn't inaccurate, but as a travel guide through cheese
land I would find this hugely unsatisfactory. You could also make a beer map, stamp The Netherlands with Heineken, Ireland with Guinness, Denmark with Carlsberg and leave it at that, but then you would ignore heaps of small breweries that make nicer, more special beers. Same with cheese; there are lots of small cheese factories that make special cheeses, but they are too small to appear on a map like this.
If you're travelling, it makes sense to discover the
local markets. You won't get your best info on the web. Try visit farmers markets, shops specialised in regional delicacies, ask local people...
And don't travel criss-cross over the map of Europe in an attempt to do as many countries as possible, as then you'll probably end up visiting clichés and there won't be much depth to your
experience.