I’m wondering who “decides” that there are highway=footway/highway=path,informal=yes in some location?
For instance, in my neighbourhood, there is a school with a park where some paths are marked as footways or paths/informal but there are no such paths on site.
Do I need to assume that the person/entity who added them used some kind of plans provided by the local government (city/province), which would make them more ‘official’, or can I safely modify them based on local observation?
You can safely modify them based on local observation. Desire paths can be difficult to map using imagery because by their nature they are going to shift over time as people respond to changes in the surrounding environment.
If a path is on a plan from some government, it is almost by definition not informal. The only exception I can think of is a document that recognizes the existence of a desire path and states some course of action to be taken on it (eg. upgrading it to a formal maintained path or putting up some kind of barrier to discourage use).
Note that there is a little footbridge ~70 metres northwest of home plate on the baseball diamond. Is that an ad hoc structure, or was it built by the local government? If the latter, does it mean the local government recognizes the path, or just that they want to provide some way to safely get across a ditch? Again, that requires direct, on the ground observation. Are people actually walking these “paths” enough to make them noticeable or did the mapper five years ago just decide to connect corners of things with informal paths?
As many of those paths were added by @ChaireMobiliteKaligrafy and not a random five-edit user last seen four years ago, I suggest asking directly. That account is very active in Quebec and likely had valid reasons to add those “invisible” paths.
These are informal paths for users of pedestrian or cycling routing engines to specific playgrounds or sport pitches. Without these, routing to a large soccer field or a playground in the middle of a park could send you in the centroid, which could be near a large non pedestrian friendly road or route you through a impassable fence instead of routing you through the park entrance and its main path before reaching the pitch. Usually, any POI or feature in a park should be connected to the pedestrian and cycling network.
In reality, people will walk on the grass to reach the pitches. You can use footway=link if you prefer. This is necessary until routing engines can route through areas, but it has been a promise since the years 2000s, so I would not count on that being available anytime soon!
Yes please do use highway=footway + footway=link for these. The tag is specifically meant for places where a virtual routeable way is needed in the data, but there is nothing recognizable as a path on the ground in the real world. highway=footway/path + informal=yes means something else. It is for a physically evident path that just happens to be informal.
