Yes, I know. Again, I read the full report. I don't think "Harmful" is an accurate summary of their position either. (At least in a layman's sense of the term; it may very well be the correct category from the perspective of Mozilla's formal standards position process.)
The more detailed summary in the full report says:
> There is a lot to consider with web packaging. Many of the technical concerns are relatively minor. There are security problems, but most are well managed. There are operational concerns, but those can be overcome. It’s a complex addition to the platform, but we can justify complication in exchange for significant benefits.
> [...]
> Big changes need strong justification and support. This particular change is bigger than most and presents a number of challenges. The increased exposure to security problems and the unknown
Read the rest
effects of this on power dynamics is significant enough that we have to regard this as harmful[1] until more information is available.
> We’re actively working to understand this technology better. The Internet Architecture Board are organizing a workshop that aims to gather information about the bigger questions. That workshop is specifically structured to collect input from the publishing community. The technical details of the proposal will also be discussed at upcoming IETF meetings. Based on what we learn through these processes and our own investigation, we might be able to revise this position.
(Source: https://www.iab.org/wp-content/IAB-uploads/2019/06/mozilla.p...)
That doesn't sound "harmful" to me, it just sounds like they're skeptical, and possibly a bit confused. The meat of their concerns also seem to be primarily political, not technical.
[1]: https://github.com/mozilla/standards-positions