Understanding this crystal connection
There is no reason why the resonant element can't be connected to a rail. 

See, for example, DOI 10.1109/JSSC.1984.1052122 A One-Pin Crystal Oscillator for VLSI Circuits, Santos et al.. 



Ignoring bias components in both cases, the circuit is really similar to the Pierce oscillator conventionally used (using complimentary transistor and grounded at a different point):







simulate this circuit &ndash; Schematic created using CircuitLab

Both capacitors must be integrated into the chip for this to work so the load capacitance on the crystal is fixed. The authors claim lower crystal dissipation due to smaller feedback capacitors, which would be an advantage in some cases.