According to the Apple Support page for FileVault, I should see some form of progress indicator when enabling or disabling FileVault, however I do not have anything appearing. The only thing my screen shows is the option to Enable or Disable FileVault, and a button that says Advanced that lets me set the amount of time before my computer logs out, and the option to require an Admin password to access system-wide preferences. I have a 2019 MacBook Pro running MacOS Catalina Version 10.15.3 Beta (19D62e). Was the progress indicator removed or is this a software issue?
If you are encrypting the internal SSD on a T2 machine (which the 2019 MacBook Pro is) then encryption is pretty much instantaneous.
You can try:
fdesetup status -verbose
See what that says.
If you are encrypting an external device where there needs to be an actual sweep of the device blocks then you should see the progress bar.