The 14 June Statutory Instrument had three requirements listed for the insurance (I don't believe this was changed from the earlier SI). It's pretty clear they have not been enforcing these requirements as many people are reporting that their policies were accepted and not all those policies cover all these items (not my issue - just a comment).

See the bottom of Page 5 of the SI - 4(d)(i) through 4(d)(iii). Image attached.

The portal, under "Required Information", lists:
- Health information (COVID19 and infectious disease related)
- COVID19 travel Insurance evidence

The FAQ page on the portal also states:
10.What insurance do I have to upload?
Non-Residents are required to purchase COVID-19 medical insurance. This has to be an insurance that can cover you while in the country in the event that you become sick and can cover your medical and quarantine costs. Travel insurance is an option.