Biasing MOSFET with Constant Current Source
It is not a preferred method. It makes for rather a 'pantomime horse' of an amplifier. But it will work.

A single-ended source follower output stage needs some method of sinking current away from the source. A resistor to ground is the usual method, though it does have the the disadvantage over current source arrangements of sinking little current at low voltage, more current at high voltage, so using more bias power for the amplifier useful power output.

For current source type loads, a more typical current source would be to use a BJT, with the base biassed to a volt or two, and an emitter resistor to ground. This has a larger output swing than a 317, and is more scalable to other currents and voltages, but uses more components, and may not be any cheaper. I have some concerns about the stability of a 317 used in that way without capacitors, as adding capacitors for stability would impact its dynamic compliance as a current source.

Given the high distortion and high dissipation of the amplifier shown, there seems to be little point in polishing that particular stool by worrying about what type of biassing is used for the output. If you want to go tube for the lolz, then go completely tube. If you want an amplifier with low distortion and reasonable efficiency, then look up some proper designs for low power amplifiers.