STR:

1. Set privacy.resistFingerprinting to true in about:config
2. Visit https://www.google.com/maps/place/San+Francisco,+CA/@37.7576928,-122.4787994,13z/ (Google Maps view of San Francisco)
3. Watch the icons over the highways (the yellow roads)

ACTUAL RESULTS:
They initially render the highway names (1, 280, and 101), and then they cross-fade to some rendering of graphical corruption.
(Additionally: if you use geolocation on Google Maps, the blue-dot showing your location renders with the same graphical corruption.)

EXPECTED RESULTS:
No such graphical corruption. They should remain 1, 280, 101.

There's a canvas-usage icon in the URLbar that I can click into, to grant Google Maps permission to read back data from the canvas. If I do that, then I get expected-results. So I think the issue here is that Google is drawing these icons using canvas, and reading them back, and we're blocking the readback, and so they end up drawing some form of garbage instead.

I've tested on Firefox Nightly 113 on Ubuntu as well as on macOS.

Not shown in the screenshot: the blue "my location" dot looks extra-broken (if you happen to be sharing your location with Google Maps) since it's substantially larger than these highway-marker icons. It renders as a rectangle of graphical-corruption, too -- just a larger one.

I can reproduce in old Nightly versions as well. In sufficiently old builds (2020-05-13 and before), the icons are solid white (still broken-looking but a bit less bizarre).

From mozregression, it looks like the solid-white-to-graphical-corruption change was from bug 1621433, and was generally an intentional change (to foil attempts at canvas-based fingerprinting, not specifically to break Google Maps).