Voted yes for exact same reason
First, while the ECU does not have a precise RTC, it has one in order to timestamp logs. It would record the crash and you can interrogate it. All you need is to compare its time to the phone time and you will get the crash time exactly down to fractions of a second. In addition to that, depending on what apps you are running the crash may also be recorded on the phone accelerometer. So the argument about "inexact time of the crash" is illiterate, at best.
Second, from a legal perspective, this should not need any new law. Existing law in most jurisdictions allows the police full and unfettered access to the car, inhabitants and cargo to investigate a crash.
Third, there is a long standing precedent basis which curtails the right not to self-incriminate yourself in such circumstances. For example, you are automatically guilty if you refuse to submit yourself to an alcohol or drug test in the aftermath of a crash. Same for speed cameras and "identifying driver", etc. The moment you get in a vehicle you wave half of your rights not to self-incriminate in pretty much any legislation worldwide.
So on the balance of things, it is better if:
1. The police does it systematically
2. The evidence obtainable through this is strictly limited by a law so the police cannot use it for fishing expeditions looking for other stuff.
If these are not in place they will do it anyway, but without any controls to limit what can they obtain and what can they use the info for.