Trainer Difficulty resetting in workout mode

It is a bug that the Trainer Difficulty (TD) seems to be resetting (to the default) when using workout mode? If not, why does it do this, and can it be changed?

Two weeks ago I I tried out the workout mode (with ERG turned OFF), and the resistance on my Kickr was significantly higher than normal. In normal riding I keep TD set at 0 as it’s more conducive to riding and training on a handcycle limiting the gear changes with very narrow power bands.

As a result of using workout mode like this, I had to ride 3 gears lower than normal - even on level terrain such as Tempus Fugit. I assume that it’s resetting the TD to 50% but it doesn’t seem as though it should affect performance on level terrain.

This is problematic as it completely changes the usage of my gears when I don’t want it to. What I want workout mode for is to display the workout data for the workout, and to create the “breaks/ segments/ laps” (whatever they’re called) in the FIT file so that it’s easier for my coach to look at the data. I don’t want workout" mode to change how Zwift or the Kickr works or interacts.

The ride(s) I completed after this one I reverted back to normal usage and everything performed as expected - my normal use of gears and resistance.

So, my question is: Why is workout mode altering how TD functions when ERG is off and can that be changed?