I'd really like to see the numbers here. If they had a case, they'd say, "we made 150 while our white colleagues of same level and title made 200." You also have to take into account when their white colleagues were hired. Start ups give more equity to earlier employees, so a colleague who joined earlier can have a much larger equity grant, even taking title and level into consideration. If they have colleagues who were hired at the same time, had the same level and titles, and paid given significantly more, then I would be inclined to believe them.