You are absolutely right.
In François Boileau's study, I found an interesting definition of the active offer and of its importance. The active offer means that the service should be visible, audible, accessible, present and of equal quality to the service in English. Those five criteria are pretty significant.
As you said, a visual message leads to an increase in the demand for services in French. When there is no indication that the minority language can be used, people naturally tend to use the majority language, especially in minority communities where bilingual people speak the language without an accent.