According to the OSx86 Project:
The problem is that OS X has an incomplete ACPI implementation which supports only a subset of DSDT. Modifying the DSDT allows the user to better support their hardware. For example, fixing Time Machine and the UUID 35 error is possible after modifying the DSDT.
Also, according to ArchWiki (which is about Linux):
A common linux problem is missing ACPI functionality (fans not running, screens not turning off when the lid is closed, etc.) stemming from DSDTs made with Windows specifically in mind.
Hence, if both the above "OS X has an incomplete ACPI implementation" and your quote "HP generally seems to write exceptionally bad ACPI code" are true, then patching the DSDT might result in a better match, and thus make OS X work better with your non-Apple hardware?