Confusion about Gaul's mines and Tourism

[Infixo]

Found by Brixter
https://forums.civfanatics.com/threads/gaul-should-have-double-mine-tourism-but-they-made-a-mistake.683397/
My final conclusion was the following:
I’d settle for normal 100% tourism but given via the modifier, remove the buggy Improvement entry and add the info to the description.

[Infixo]

It is a bit more complex than I'd thought initially.

1. The EFFECT_ADJUST_CITY_TOURISM doesn't give tourism by itself - it needs an existing source of tourism. That is why Firaxis added an entry to Improvement_Tourism table.
2. The ScalingFactor in Improvement_Tourism table is ignored. The game always generates Tourism equal to the source yield (e.g. 3 culture improvement always gives 3 tourism, no matter what ScalingFactor is).

So, to actually achieve a desired effect i.e. tourism from mines just for Gauls, one needs an effect that can generate tourism by itself. There is only EFFECT_ADJUST_CITY_IMPROVEMENT_TOURISM that produces tourism from all improvements unfortunately (used by Golden Gate).
TEST: this effect also works only with the already existing tourism i.e. it multiplies existing sources, and doesn't create any new tourism.

Summary: there is no modifier to grant tourism to an improvement. The Improvement_Tourism table must be used. It means that no extra modifier is needed for Gauls. BUT: it would be prudent to modify respective texts that are related to mines getting culture.