Suggestions for a local, file-based, locator will only be available for those created with the Create Locator tool (enabled by default).
The Create Address Locator tool does not support suggestions for a local, file-based locator, and only supports suggestions when shared as a service. So you could test sharing the locator you created with the Create Address Locator tool to Portal, then bring in the geocode service (not the local locator) to ArcGIS Pro and test the suggestion functionality there.
I do understand the point you are making though Bryan, searching for "606 Main St" does not yield any candidates with unit numbers, and you would need to actually include the unit number in the search, e.g. "606 Main St #100". I thought the issue was that you were searching for the address with the unit number and still not returning any results.
I cannot say for certain that what we are seeing here is expected behavior, but I see the same on my end. Bryan - I'd recommend we work through your Support case to maybe see if we can get an enhancement logged to provide similar functionality to what you're seeing with the Create Address Locator tool with the Create Locator tool (ability to search for the base address and see all associated subaddresses as well). I'll track down your case and work with the analyst to see if we can get something like this logged.
Best regards,
Eric