Long story short it is unacceptable.
Why can t you use pex for tub spout drop.
I m certain they do not want you to use pex from the drop ear to the tub spot but you could probably use it between the faucet and drop ear.
In areas that are concealed like under a kitchen sink or vanity cabinet you can eliminate a joint by running pex supply directly to the shutoff valve.
Why can t you use pex for a tub spout.
Use a drop ear bend support to hold the tubing in a tight bend right.
How did this project turn out.
Also a lot of tub spouts have installation methods that only work with copper stub outs.
You can connect a compression type shutoff valve to the one half inch copper stub out and then connect your fixture.
If you use pex for the tub spout when you turn on the water to the tub water will back up through the shower head due to the reduced inner diameter of the pex it s called stacking.
A lot of manufacturers are very specific about this and i ve seen it hundreds of times.
Copper is the only professional installation material.
With a built in diverter you could use a pex drop eared ninety degree female adapter and a nipple but that is more trouble than it is worth.
2 reasons i learned.