An order to preserve evidence is only as good as the honesty of the people involved.
I'd say it's only as good as the seriousness with which you plan to enforce it.
It's like a kid getting picked on by a group of bullies. He can tell them to leave him alone all he wants, but they're not going to listen... Until he lays one of them out. Then they'll realize that there are actual consequences for messing with that kid.
I remember when Hillary Clinton was under a "preserve evidence" order... before she smashed multiple cell phones and wiped a laptop hard drive.
An order to preserve evidence is only as good as the honesty of the people involved.
If you want to preserve evidence, then send state troopers in, confiscate it, then hold that evidence.
I'd say it's only as good as the seriousness with which you plan to enforce it.
It's like a kid getting picked on by a group of bullies. He can tell them to leave him alone all he wants, but they're not going to listen... Until he lays one of them out. Then they'll realize that there are actual consequences for messing with that kid.