Why no option to customize run workouts?

Does Zwift not allow for us to customize our own RUN workouts?

This is from the Zwift Knowledge Base:

Can I create my own run workout?
Currently, you cannot create your own workout in-game. However, if you have TrainingPeaks connected to your Zwift account then your workouts will appear in Zwift. They’ll show up in your workout selection screen. Just make sure your workout is set to the same day you are running on Zwift.

Here is a link to the article: https://support.zwift.com/hc/en-us/articles/360000701251-Running-FAQ?section=360000168612

Link to the Zwift Runner’s Guide: https://support.zwift.com/hc/en-us/sections/360000168612-Zwift-Runner-s-Guide

Thanks.  I actually built a workout in Training Peaks, and it isn’t populating into Zwift.  I’ve reconnected the accounts a couple of times today to see if it shows up.

My understanding from another article is that the workout has to be built using certain parameters.  I found this:  “Only RUN workouts that are based on Distance and threshold pace will work.”  I was hoping to get around that by building directly within Zwift.