It is not the AVERAGE or typical experience, but it happens. And this is not the first time it has happened.
When NT4 was new, it became infamous for crashing and corrupting the system files if there was more than one primary partition. That's perfectly legal under DOS partitioning rules (which are real even if they are not readily found) and normally, there was one primary partition on each disk, especially when someone had added a new disk and just "moved other" the old one. Resulting in two disks, one primary partition on each. Under NT's "preferred" configuration, there should only be one primary partition, on the boot drive, period. MS took some flack for failing to support standard drive configurations.
I have experienced MS's own tech support repeatedly being unable to correct a Win10 "update crash" caused specifically by Win10 not recognizing legacy drive partitions, and seen the third-party software fix that with no problem. When boot management was still done with BOOT.INI and standard configuration files, it was just a matter of pointing the boot drive to 0 or 1 or 2, and if the new system was counting or ignoring legacy or hidden partitions--no problem, you just changed the drive number and told it where to boot from.
Win10? Nope. new and improved, kiss of death is lurking there.
I'm sure you've never been bitten by a rattlesnake. Nevertheless, they are known to be out there in the wild, and sometimes to bite folks.
Yeah, forty (four hundred?) million lines of code and there are sure to be some errors. But being unable to escalate internal support and address the issues, really never has been excusable.