Apparently, they have left out v02.99 Rev.A (sp73099) out of the list from the https://support.hp.com/us-en/drivers/selfservice/hp-compaq-elite-8300-convertible-minitower-pc/5232845 database. This is the prerequisite to flash this BIOS prior flashing the BIOS higher than this revision such as the lastest revison 00.03.07 Rev.A (sp88543) listed.
Anyone attempted to flash with greater than v02.99 Rev.A will not able to flash the BIOS.