"Cracked" is a very broad term that can be thrown around too easily.
There are so many questions;
-Did the police lie about the phone being cracked in order to make the suspect confess?
-Did the police found a note with the password, and unlocked it?
-Did the police find the prints on the phone matching the keypad code?
-Did the police unlock it by using a fingerprint mold?
See also:
https://discuss.grapheneos.org/d/17652-an-article-describing-police-using-a-fingerprint-mold
(Now people can use a 2FA fingerprint autentication, but you can also set autoreboot to 10 min or so)
-Did the police look at surveillance camera's of the suspect typing the password?
-Sometimes, they give the phone back temporarily for a "call with the laywer", when they put a special screenprotector on there to see what people typed, or checking camera surveillance in the holding cell.
And there are many more capabilities.
It is hard to imagine they "just cracked" the phone.
The Dutch and Flemish police have alot of funding, money and tools at their disposal, but if you set up a GrapheneOS phone securely with a high threat-level in mind, you should be okay.
If you treat is as a phone with a low threat-level, then I'm not sure what would happen, but there are many ways around security other that just cracking it, at many occasions it is not required.