The TDA7000 converts the RF at 100Mhz (ish) to an IF of 70khz.
The demodulation (using a PLL, the datasheet calls it an FLL, Frequency Locked Loop) takes place at a low frequency 70khz, not 100Mhz.
In a receiver of reasonable performance, the incoming RF is converted to the IF using an oscillator whos frequency is determined by a phase locked loop.
Demodulation of the FM can take place at the IF frequency usin a variety of methods, one of which is a phase locked loop.
Demodulation of the off-air signal at 100Mhz is not practical in a radio receiver.
It may be quite possible to build one, but its performance will be limited.
JimB