I'm glad to hear you solve the problem, if you have any issue about SharePoint, you are welcome to raise a ticket in this forum.
By the way, since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others.". So, I would make a brief summary of this thread:
[How to Add Show/Hide conditional formatting to column in Lists]
OP want to format a date column to show or hide depending on what option is picked in a choice (not multiple selection) column. It is not working and only hiding the column instead of the command given.
OP used this code to format the column I want to show/hide: =if([$Category] == 'Product Management', 'true', 'false')
OP actually figured it out. When OP created the choice column, it had a different name. OP edited it later on. When coding, the system only recognizes the column for its original name when it was created and not the new edited one.
You could click the "Accept Answer" button for this summary to close this thread, and this can make it easier for other community member's to see the useful information when reading this thread. Thanks for your understanding!