HP says the "flashing" is a way to update and fix the BIOS.
Hello and welcome to the forum.
That is correct, Flash or Flashing is a term used to describe updating a system's or a single device's firmware to something more current and up to date. But, as you seem to already know, does not happen by accident or automatically generally speaking and I would think that HP would know if they have some type of auto update utility on your system that would actually evoke a BIOS Flash. But any piece of hardware that includes an EPPROM can generally be written to or flashed (your CD/DVD, your NIC, your GPU, etc.,) but again these things do not usually happen automatically.
How is your system now? Are you seeing any negative side effects...