What are your current Goals settings? (ATP, Athlete Type, etc.)
What is your status stars count?
Post the activity charts for your Z2 ride and that interval workout.
Freshness Feedback is the right tool to use when calculated form does not match how you feel.
I don’t think you necessarily need to use it based on what you’re saying. Post the info above so we have a clearer picture of your training.
Polarity ratio in Xert doesn’t refer to “polarized” training but you are accomplishing that based on your 5/2 week description.
See this post – Polarity stats - #3 by ManofSteele
There is a difference between 97 XSS in 90 minutes (Moderate) and 90 XSS in 60 minutes (Difficult). Think XSS per hour.
Specificity is a factor too. Do you have a grasp of that concept as it relates to the difficulty rating?
Reference –
Freshness Feedback slider
Difficulty Rating – Xert (baronbiosys.com)