Hollow points are primarily used by the police for their penetration (or lack thereof)—not their stopping power. As you note in your parenthetical, this would entirely negate that.
That being said, there has been a lot of evidence that shows that HP rounds penetrate further than conventional wisdom would expect, and it likely gives LEOs a false sense of security when firing in an apartment complex or into crowds.
> Hollow points are primarily used by the police for their penetration (or lack thereof)—not their stopping power
I suspect that this is more true of the public justification for their use than the motivation (not saying it's not part of both, though.) Politically, “it reduces risk of accidental injury to bystanders” is probably more palatable, especially to the factions most likely to object to police-preferred gear, etc., than “it makes the injuries to the people we target more grievous”.
That being said, there has been a lot of evidence that shows that HP rounds penetrate further than conventional wisdom would expect, and it likely gives LEOs a false sense of security when firing in an apartment complex or into crowds.