Almost - but not quite.
The 819-line French standard was a monochrome standard, and it went into use right after WWII.
Aside from a handful of experimental broadcasts, SECAM color never used 819-line. SECAM in France and neighboring European countries was always 625-line, based on the CCIR 625-line monochrome system that was the European standard after WWII everywhere other than France, Belgium and the UK.
So the 819/625 line switch on this set actually chose between legacy monochrome 819-line French broadcasts, legacy monochrome 625-line that might have been seen in border areas from the Netherlands, Germany, Switzerland or Spain, and 625-line SECAM color broadcasts from France.
There was also some 525-line SECAM color in French territories outside Europe, including the Caribbean, which means yet another variety of multi-standard sets for those areas.