That sounds like the Swedish rule (except for parliament where it is eight per cent, but lowering that to five has been discussed).

In effect, in larger constituencies, there will be safe seats for large parties. If Labour and Conservatives each take 35% in South East they get about six seats. For the first name not to enter six candidates need to not only get more then number one, but also more then five per cent of the party votes each. And since it is a large constituency, with lots of people that means that six lower ranked candidates need to get their message out to lots of people.

On the other hand, all seats in Wales can very well be sorted on number of preference votes. And small parties has no safe seats as it only takes one other candidate to get more votes in order not to elect the top name where the party gets one seat. So it is a non-sensical barrier that only makes sense from the perspective of large parties (guess that is why it is proposed).

Btw, I can't get to the pdf. Even with adjusting for the link being incorrectly written. Anyone else can? Is it UK only?

Sweden's finest (and perhaps only) collaborative, leftist e-newspaper Synapze.se