More often than not, the changelog just states "performance improvement" or "bug fix", without any detail on what they've done.
For example, I've been bitten before by Dell due to plundervolt updates that removed the undervolting capability under the umbrella of "security fixes".
They can but the data on the chip is a combination of machine specific identifiers, config data, and BIOS code. If you chip flash it you have to get an image from some sketchy place and it will nuke your serial number etc. You can also have problems if your RAM is made by a different manufacturer. Chip flashing is a last resort.
For example, I've been bitten before by Dell due to plundervolt updates that removed the undervolting capability under the umbrella of "security fixes".