Why did Rigny command from a frigate?

Was Rigny's frigate flagship a practical choice for speed, or a sign he could not handle a ship of the line?

Limited experience is the favored explanation here: Rigny was more comfortable in frigates, and his Allied colleagues distrusted him on larger ships.

A fast frigate could make sense for errands and signalling, but that was not the main explanation offered here. Rigny had spent much of his distinguished career with land forces and had little experience handling ships larger than a frigate. He remained aboard Sirene because that was the type of ship he knew best. Codrington and Van Heyden interpreted the choice as a command limitation serious enough to keep him from leading the coalition's heavier ships.