Not surprised in the least. The funny thing was, when our station had programming targeted to under 12 (and thus subject to the tighter rules), we were always sold out with advertising - both weekday morning and afternoon and Saturday morning blocks. When we made the switch to 13-16 targeted programming, most of the advertising went away. We could sell more, but few were buying.
Of course, this will also dry up a source of revenue for the FCC by limiting $10,000+ fines for violations by broadcast stations when they messed up and went over the limits or accidentally aired a host-sell ad.
I suspect at some point the pendulum will swing and all E/I programming will have the limits.