While I see your viewpoint about Manjaro keeping up with the newest releases software wise, I don’t think kernels should be lumped into that category.
If Firefox stops working on an update the user hopefully has an alternate browser installed. If wine quits running no great loss.
If your kernel stops booting, that is often beyond the knowledge level for new users to remedy on their own. New users often delete the old kernel when they update and have no alternate kernel to boot to.
There should really be a message displayed in that regard to my way of thinking. I mean, if MSM is giving recommendations to perform an operation with potentially negative consequences, it should also give a recommendation to maintain at least one backup kernel. I think if MSM is going to be giving recommendations at all, it should at least balance the advice it is giving with some safety based recommendations.