Hi Cash,
Thanks for providing the detailed information for us which made my test more convenient.
I tested at my end by using the Filter feature in Edit View setting, but I have the same result as yours. (The items were not filtered in the result.) Then I found that we can use the Filter by feature of the column as a workaround.
Since we can reproduce this issue at my end, we assume this issue is more complicated than we thought. And we are unable to investigate this issue at my end due to the limited resources. I sincerely suggest you contact IT admin to raise a ticket in Office 365 admin center, and I will provide a summary of this issue in PM link for you. It will benefit the agent to speed up the process. Your understanding is highly appreciated.
For more information, please refer to: Get support
Best Regards,
Ivy