Why the difference? The simple answer is that one group is trying to communicate accurately the facts, while the other is more concerned about sowing mistrust, even if it is not justified. It is not difficult to guess what it is.
The Report: e-cigarettes - Evidence Update
Risks of E-cigarette
The report is available in its entirety here (https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/454516/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England.pdf), but with more than 100 pages , It's probably not something that most smokers or vapers really want to read in their entirety. However, it is very broad, and addresses many of the exaggerated risks of Vaping frequently repeated by the media.