Sure there can.
You can have personal standards, school standards, state/county standards - and so on.
Having a set of standards suggests you've put at least a little consideration into what you consider the minimum level of acceptability.
What this was kind of leading to is that a person of at least close to average fitness (or above) stands a decent chance against any other average kind of person.
Add in a bit of training in restraint, the authority of the uniform (which does actually exist) and a few other tools and that "bit below average" person is well above average.
Then also consider that "street fighting" is pretty much the last thing a police officer should really be engaging in.
Take all that, add in the "survival rate" (whichever one you choose, the percentage is close enough that it doesn't matter) and you get to my opinion on the initial subject of the thread...
No.
Police should not be compelled to train in any specific fighting art, whether BJJ or not. What they do (in combination with everything else) actually works well enough in the very vast majority of cases.