For example : all  the blocs represented in the presidential election will present a candidate in every district, so : one far left, one Mélenchon, one PS/EELV.
Also, they give an arbitrary boost to sitting candidates. This is not a good election for sitting candidates.

To be fair, all they can do is model. Neither the candidates nor even the forces in presence are clear yet. But the result will look nothing like that.

With this model they get only 52 to 78 left candidates surviving the first round, and only 34 to 51 elected.
Those numbers are frankly ridiculous, bearing in mind that .  The party structures will sort something out, to avoid a complete murder/suicide. Even if they don't, which is not impossible, left-wing voters are smarter than that. They will choose the locally-legitimate candidate, as they did nationally in the presidential, which is why Mélenchon got close to qualifying for the second round.

However, En Marche has the huge advantage of being in the middle. In any hypothetical four-way first round, it's likely (depending on the abstemtion rate) that two or three candidates will qualify for the second round. Assuming that EM is one of them, and that the LR or left candidate is eliminated, they are pretty much guaranteed to get the benefit of the eliminated candidate's votes in the second round.

So it would not be surprising if EM got something close to a majority. But it would be very surprising if the left were to be so completely wiped. Especially with the FN set to take a nosedive in the second round of the presidentials.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}