When was the last time a Sales Manager rolled up the CRM Forecast and sent it to the CFO without Modifying it? -

There’s a very strong possibility that the data is out of date since the sales reps never seem to update it on a regular basis.
You can’t validate the accuracy of the data
The data may not reflect the actual reality of winning a deal. Being at the Proposal Stage doesn’t necessarily mean an 80% chance of winning the business. Likely, 2 of your competitors have also submitted proposals; it doesn’t make sense that all 3 of you have an 80% chance of winning the business.