I honestly think this is a great decision.
For one, the old system has been in there since we had connection. Now connection was a mostly useless thing, but it did keep people who got most of their points from grading from getting too too far above the graded, since you could not apply most bonuses to it, and it was the stat that determined Shikai, awakening, bankai, and all that fancy stuff. With its removal, the grading bonus became infinitely more valuable, seeing as how it was a direct form of power and kai strength. It went from a decent boost in rei, to a literal extra 4000 words of points, and 6000 if you had both staff and grading. That's scary, from the eyes of someone who does not write that much, and probably the eyes of people who write normal amounts, too.
For another, with the ability to get it without writing, it takes a lot of pressure off a grader. Not everyone updates every week, myself vastly included. And some of these people are the usual graders. Usually, if a grader did not write, then they would shove the duties off on someone else to keep those points from being wasted. This person probably did not know about it until the Sunday or Monday that they entered chat, and would have to scramble to find and read absolutely everything that their group had posted throughout the week. Now, even if the grader did not write, they can still grade and receive a bonus, and will only get other people to grade for them if they genuinely do not have he time to grade, allowing the age old question of "who's grading?" have a more consistent answer.
And on the "irregular" payment, I looked at the dates that Will said it had been updated, and the furthest it was was about 23 days. Now, while that seems like a long time, it really is not. Staff only has to work once every 14 days at most, and that never feels like a long time to get reviewed. Also keep in mind that said 14 day restriction is only for the 1-10 submissions that accumulate over time, while everyone is getting kan all the time. I'm pretty sure that if I was not as lazy as I was, I could look through the achievements thread and find a great deal of kan that I am owed.
As for "disingenuous," I'm afraid I don't see how this is any less sincere than the old reward. Kan is less direct power, but more flexible, letting you buy kidou slots, item slots, resubs, credits, collab bonuses, stat changes, and fun little items. If you really want more rei, than 100 kan gets your secondary PC 1000-10,000 more reiatsu, allowing you to gain even more from the new bonus (well, once, but thats over a month of old bonus into one week.)