That's the difference with the presidential election where the second round is a run-off between only two candidates who got the most votes during the first round.

For the legislative elections, all candidates who get a number of votes of at least 12.5% (1/8) of registered voters can run in the second round (and then the FPTP system applies).  

As I mentioned in my diary 5 years ago, 3-way or even 4-way second rounds that were a rarity during the 1970s and 80s have become more prevalent with the rise of the FN as a third major party.