@Michael_VanHatten while I am not the employee who said in the forum your problem would be fixed in 3.0, I am the one that tested and verified BUG-000131693 is working in Pro 3.0.
Can you please give more details about the errors you are experiencing?
I just retested a scenario like what you described, using a ModelBuilder tool to select some features and calculate a field, run on a schedule. This is completing successfully for me, as long as I do not have the layer/table open in Pro, since that would cause a schema lock with the external scheduled process which is trying to update the data out in Python. You should also double check that if you are using a layer as input to the selection tool, that the project is saved with that layer, otherwise again the external process will not be able to locate what you want to use as input (there are warnings about this in the scheduling UI button, and in the documentation).
So here is what is working for me. I have a dataset, which has 10 or so STATENAME values. I want to select and calculate a field only for those with STATENAME=Wisconsin. So I perform the selection against the data path, then send the result to Calculate Field. The calculation I perform is some basic text, WI, plus a timestamp so I can definitely see that the calculation is being performed at the time that the scheduled process ran.
You can see in the History >Geoprocessing > Scheduled section I have one time that the scheduled process failed. That was for the schema lock that I mentioned before, as I had the data open in Pro, and it could not perform the calculation while the data is locked for use in Pro.