I am in the nursing profession & have a special interst in this topic.
Luthier reports the game caused "wide-scale epilepsy failures when tested". This suggests a high incidence of
photosensitive epilepsy (PSE) was encoutered amongst game beta-testers. In contrast, the incidence of PSE across Great Britain has been reported to be about 1.1 per 100,000 persons (0.0011%) [Quirk et.al. 1995].
The decision to impliment an "epilepsy filter" is presumably based upon Luthier's anecdotal observations, rather than the scientific evidence. The low incidence of PSE in the community does not seem to justify such a decision.
References
J. A. Quirk, D. R. Fish, S. J. M. Smith, J. W. A. S. Sander, S. D. Shorvon and P. J. Allen, Incidence of photosensitive epilepsy: a prospective national study. Electroencephalography and Clinical Neurophysiology
Volume 95, Issue 4, October 1995, Pages 260-267