I worked with JWP to solve this issue for user Giud, and eventually we got there. FF8 is a NIGHTMARE to debug. The optimizer being on without stack frames is only the start. This may be useful to those with epilepsy. Use HextEdit (or other hex editor) with the following:
FF8_EN.exe
{For certain flashes like critical attacks
{1067BC = 90:5
{Disable all battle flashes
1712C0 = C3
When using HextLaunch (memory addresses), it is
{For certain flashes like critical attacks
{5067BC = 90:5
{Disable all battle flashes
5712C0 = C3
If you only want specific critical flashes to be disabled, move the curly bracket { over the second entry and remove it from the first.
This is for the English Steam version. Other versions will need new addresses.