It's more of a problem this year than it will be in the future, because it's supposed to use two year's worth of competition results, but the federations and skaters did not know about it last season in time to maximize the number of skaters sent to senior B events.It is always easy to blame the rules, but if a federation finds themselves with a good skater who still has not posted a qualifying score, they really need to blame themselves (or maybe the skater/coach, if they were given opportunities and did not take advantage of them). They have all known about this rule all season.
Now they know.
For small European countries, sending their best skaters to senior Bs is not much hardship.
For small countries in Asia, Oceania, Africa, it means paying for extra long trips in addition to or instead of the long trip to 4Cs. But the small skating countries probably only have a few skaters capable of meeting the minimums anyway.
For countries like the US and Canada and Japan who may have >20 age-eligible senior skaters capable of meeting the minimums and deserving a trip to Four Continents, they may not be able to predict a year or two in advance who's going to place high enough to earn a 4Cs slot that year.
Even if they make sure to send 20 ladies to either junior or senior fall events, what happens if the one who was 21st on the list for fall assignments based on last year's results has a breakthrough season and ends up 3rd at Nationals?
And of course injuries that take a skater out of the fall season can also mean no trip to 4Cs that year.
Given the tight time frame between Nationals and 4Cs there may not be time to send that skater to a winter senior B event even if an appropriate one exists. For Worlds there's a little more leeway if there are enough winter B events. This rule will make those events more valuable.