English is not my native language but I disagree with your interpretation that summoning a faerie makes the gauge increase. I would understand the same if the wording were
The Faerie Gauge is increased when a faerie is summoned or an Aetherflow action is successfully executed.
But an "and" is used, not an "or".

"In/during combat" should be added though, as it is in the description in the other three languages.