Maybe stating the obvious here, but this is also dependent on what else you do. To wit, I made very good deadlift progress (going from 315 to 505 in a little over a year) while deadlifting much more frequently than this, but 1) I also was not squatting at all for most of that time and 2) many of my deadlift workouts were fairly "easy" - lots of medium singles. And I guess I'll also add a point 3) what works for people going from 300 to 500 may be very different than what will work to get them from 600 to 700.
(I know this is in the "Powerlifting" section and thereby we could assume that this advice need be specific to people training for a full meet, so there are probably few non-squatters here, but even squatting 2x per week vs 1x per week probably makes a big difference in whether deadlifting 1x per week or once-every-two-weeks is what works well)
Point is, I think that people who do lots of squatting and other assistance work probably don't need to deadlift much and, as you noted, might make very good progress pulling once every 2 weeks. I also think it's a semi-viable approach to do a little more pulling and less squatting.