Unclear why a filter matches only after adding `||`

[philipp-classen]

Context: https://github.com/ghostery/trackerdb/pull/437

Given the following URL:

https://www.bing.com/maps/geotfe/comp/stl?v=9.26&og=2550&idx=524&oidjs=&features=ci

it is not obvious why this rules matches ...

||www.bing.com/maps/geotfe

... but this does not (without leading ||):

www.bing.com/maps/geotfe

In my understanding, both rules should match. I also did match after adding $1p or $3p to the rule (e.g. www.bing.com/maps/geotfe$3p).

Could be a misunderstanding of mine, but it could also be a bug in the matching logic.