Yes, the strat firms are feeders to the top schools, moreso than other types of consulting firms.
Regret isn't particularly productive. Make the most of what you have now, and the experience that you've had.
There certainly has been people from econ/litigation consulting getting into the top b-schools -- the key is being able to convince the adcom that you are more than your job (the adcoms are familiar enough with this segment because it's not like b-school applicants from econ/litigation consulting are rare) -- what is apparent is that you're detail oriented and analytical (especially with numbers). What isn't as obvious are the interpersonal and team skills (which is what you'll have to really emphasize).
Beyond that, it's pointless to worry about how other types of consultants fare. Focus on you and what you can do.
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