I have now verified that I'm running the latest BIOS version and that it must have been auto updated by the Windows Update system.
I have also found two articles describing all updates for Surface PRO 4 and Surface PRO (4 2017).
They clarify that the newest graphics drivers are 21.20.16.4647 for PRO 4 and 22.20.16.4749 for PRO 2017 which perfectly explains why only some of us have got the driver update.
https://support.microsoft.com/en-gb/help/4037238/surface-surface-pro-update-history
(pro 4 2017)
https://support.microsoft.com/en-gb/help/4023489/surface-surface-pro-4-update-history
(pro 4)
22.20.16.4749
required to support Windows Mixed Reality features. (Graphics 620 only)
21.20.16.4627
improves DX12 and power performance.
20.19.15.4463
improves system performance in some applications.
20.19.15.4409
improves the overall stability of the graphics driver, resolves screen flickering in several popular applications, and cases where the display does not reinitialize correctly after the device resumes from sleep or hibernation.
20.19.15.4364
improves display stability, system stability and battery life.
20.19.15.4326
improves display stability.
20.19.15.4308
addresses some display issues, including some scenarios that result in screen flickering.