On iOS at least, if you’re concerned about police breaking into your phone, you should be using a high entropy password, not a numeric PIN, and biometric auth is the best way to keep your convenience (and sanity) intact without compromising your security. This is because there is software that can break into a locked phone (even one that has biometrics disabled) by brute forcing the PIN, bypassing the 10 attempts limit if set, as well as not triggering iOS’s brute force protections, like forcing delays between attempts. If your password is sufficiently complex, then you’re more likely to be safe against such an attack.
I suspect the same is true on Android.
Such a search is supposed to require a warrant, but the tool itself doesn’t check for it, so you have to trust the individual LEOs in question to follow the law. And given that any 6 digit PIN can be brute forced in under 11 hours (40 ms per entry), this means that if you were arrested (even for a spurious charge) and held overnight, they could search your phone without you knowing.
With a password that has the same entropy as 10 random digits, assuming no further vulnerabilities allowing them to speed up the process, it could take up to 12 and a half years to brute force it. Make it alphanumeric (and still random) and it’s millions of years - infeasible within our lifetime - it’s basically a question of whether another vulnerability is already known or is discovered that enables bypassing the password entirely / much faster rates of entry.
If you’re in a situation where you expect to interact with law enforcement, then disable biometrics. Practice ahead of time to make sure you know how to do it on your phone.