All good instructors and coaches must be serious students of their craft and this requires demonstrated performance at higher than novice levels. Sadly, within the firearms world this higher level performance is rarely required or found outside of organized competitive shooting. Regardless of the instructor or coaches background (claimed or real), this is reason enough to demand some sort of reasonable level of success in something like competitive shooting, if only to demonstrate the person is capable of doing more than merely qualify.
If you’re foolish enough to believe a military or police service record is enough, watch this video. Skilled people will note his demonstrated gun handling and shooting and realize he wasn’t worth considering, regardless of the claimed experience.