Fermenter Recommendations

The seal doesn’t matter during fermentation. You want to cover the fermenter during fermentation so wild yeast and other airborne bugs cannot drop from the air onto your fermenting wort. You also want to make sure there is no way for fruit flies to enter (if these exist in your area). After fermentation it is good to have a tight seal so that the beer stays under a blanket of co2 until bottling or kegging.

Tx  alestateyall, this is a good explanation.

You are correct.  The batch can ferment perfectly well even if the lid doesn’t seal.