I’m an active German Moderator since 2015 and this rule with 500 subs/segments was already valid when I started here.
German teams are not that big, in average between 8-16 subbers, depending on the weekly release and the number of episodes. And we are working different than Spanish teams. Each subber gets a designated part per week and for every week we got a deadline. This is not a must, but most teams are working with that condition. A few teams are working without a deadline and some teams don’t work with designated parts, mostly for older dramas with lots of episodes.
When you’re used to moderate this way, it’s not that stressful. Before the 5 projects limit quite a number of moderators had between 5 and 10 projects with good quality subtitles. We have a huge lack of good editors and such, who complete a drama. Many underestimate the workload, when you’re editing thoroughly. So it’s not the question, if an editor deserves its position, but to find just one editor altogether.