I have never had this issue before build 2004, I'm on the insiders list but staying on retail builds. I've also not seen that using "dfrgui" the defrag window is actually trying to defragment the SSD. When
I use manually use "optimize" it says "n% trimmed" but the status is not kept, right after that when leaving and restarting dfrgui it says "needs optimization".
I got build 19041.264 installed on April 17th ... I mentioned this problem (and a few others) in the feedback hub, without getting feedback :-)
I'm only seeing this issue if I go to Control Panel>Security and Maintenance and run the maintenance manually.
If you run the maintenance Control Panel>Security and Maintenance while also having the Optimize drives (defrag/optimize drives) open you will see it defrag then trim right in front of you.
You will only see it of you have both open at same time and do manual maintenance via Control Panel>Security and Maintenance. You will catch Windows doing it. Open Control Panel>Security and Maintenance and Optimize drives side by side and run manual maintenance
(Control Panel>Security and Maintenance) and you will see it defrag briefly and then trim.
If you just open 'Optimize drives' only and select optimize then it will just trim it only.