Students saw they had received 2.62 out of 3.
I assume they did see that at the workshop main screen once the activity has been closed (those two big boxes with final grades).
If I remember correctly the decimal places configured in the workshop settings form, affects decimals displayed on the workshop reports during the assessment and evaluation phases. Once the workshop is closed, the grades are pushed into the course gradebook and the stored value is then being displayed. The particular workshop grade items in the gradebook have their own decimal places setting, and that one is respected in the closed phase.
In other words, as long as the workshop is in assessment or evaluation phase, all the individual submission and peer-assessment grades are stored in a "temporary workshop gradebook" for that particular activity only. Once the workshop is closed, the aggregated final grades are written into the official course gradebook. These two gradebooks are two separate systems, each with its own settings for decimal places.