That problem is already solved though by the FDA (and clinicaltrials.gov). Once you submit your documents to the trusted authority you can't modify them without it being super obvious.

This is only done after all data has been collected an analysed (from multiple clinical trials!) and when a company is looking for market authorization. So clearly if anyone wants to alter their data, they would do this prior to submitting their study dossier to the FDA. This has happened time and time again....

It is therefore crucial to make sure data cannot be altered AS SOON AS IT IS COLLECTED. At this point, one would not yet know how to alter the data and if that would steer results in the 'right' direction (researchers are blinded for instance).

So I definitely see value in creating a cryptographic hash of a data point, and immediately registering it in some immutable database (which could be blockchain, or a different solution I suppose)