The idea is that new players and low win-rate players would be in the same tier. They would play against other new players and low win-rate players. This would mean sprouts would start off not running into curbstomping premades and would have a chance to enjoy the mode and improve, rather than the current situation where they get smashed into oblivion.
Similarly, high win-rate players would be placed in teams that face off against other high win-rate players. Since those who play in premades have outrageous win-rates, this would filter them all into the top tier where they would play each other. This is precisely what Olivia et al claim to want. High-quality matches a la JP. If true, they should support this proposal.
This strikes me as a fairly standard method used by PvP in other games to ensure players are pitted against others of comparable skill. League springs to mind. I wouldn't regard it as a ladder that needs to be climbed, although it's fine if some choose to do so. Just a method of creating more balanced and competitive matches.
I have no doubt members of the Discord Mafia will find some way of abusing the system. That's what they do. But the general principle is that FL currently includes players of massively different skill levels, either because they are new, don't give a rat's-synonym-for-a-donkey, or at the other end of the scale will go to any lengths to maximize wins. I can't think of another game in which the "fun, casual, entry-level" PvP mode expects sprouts to contend with meta-stacks comprised of players with nosebleed win-rates and 10k+ matches of experience.
The current system dooms the majority of players to endure porridge that is either too hot or too cold. I want it changed.