Commitment value is changing after sprint start.

Problem

The Commitment value is reducing after the sprint start. Checking the documentation about the Velocity Chart, it's stated that:
Commitment: The gray bar for each sprint shows the total estimate of all issues in the sprint when it begins. After the sprint has started, any stories added to the sprint, or any changes made to estimates, will not be included in this total.
However, if we change the Story Points of an issue (even after completing the sprint) the value of the Commitment is changed.

We tested on two vanilla instances over the "Create Project with Sample Issues". Kindly follow the Commitment reduction on the attached images.

Environment

Jira 8.15.1
Jira 8.7

Steps to Reproduce

• Create a new Sprint
• Add issues to the Sprint
• Start the Sprint
• End the sprint
• Change the value of the Story Points with one of the issues that belong to the sprint to any value
• The Story Points of that issue will stop to be considered on the Velocity Chart

Expected Results

After starting the sprint the Commitment should be the same forever.

Actual Results

The Commitment changes if we change the Story Point of the issues that belong to the Sprint.

Workaround

No workaround found.