see that 1M feedback resistor? bias trim.
if you sort of let your eyes drift out of focus and look at an older datasheet that has the CMOS internal workings illustrated of this 4001 gate (like my old RCA or NatSemi databooks,) you may see it looks a darn sight like a FET-input op amp. indeed, it sorta is. you in fact have some extra steering FETs on the inputs that allow using both inputs as +VSS to 0 VDD logic, and it's good up to about 10 MHz on a really good day, 5 MHz or so worst case. I first saw this in a mid-70s frequency counter input schematic, but apparently been in use for a while.
put a crystal in that loop, you have an oscillator, which is a much more common look at a 4001 gate to a ham. in order to get anything to oscillate, there has to be some gain and positive feedback. selected 455 KHz ceramic resonators above and below 455 switched into that loop, you have USB and LSB for a simple receiver. it's decently stable. I've been meaning to drop one into a Zenith TransOceanic for quite a while, but I keep getting called away...
the circuit has been around long enough to get into many, many little publications.