Standard Map Features

I’ve just seen the same thing. This only happened after the last map update (I assume as I definitely had footpaths, but not contours, before)

The footpaths are certainly known by the watch, even if you can't see them on screen. If you let the watch suggest a walking route to a destination, it will use them.

A few weeks ago I had a job in a city in UK. Between my workplace and my hotel was a somewhat large forest, which I could walk through or walk around to get to/from work. 

The first few times my watch suggested a route through the forest, I simply didn't believe it and instead took the major roads, because there was no real path at the place where I was supposed to go into the forest. But eventually, I caved in and started to follow the route suggestions from the watch, and the paths were actually there. Quite often, they were only 20-30 cm wide, with plants growing over the path from both sides, but the watch knew them!

Footpaths come into view at 500 ft on my EU maps.

I understand that the maps use a combination of known trails and heat maps to derive routeable tracks/courses.

That is my understanding too. As far as I know, Garmin uses freely available maps (OpenStreetmap?) and bakes information from their heat maps into those maps before releasing them.

But my point was that - at least as I remember it - the paths weren't visible on screen when I just zoomed into the map on the watch. I had to use navigation to "reveal" them.

You can also switch contours on in the map settings