I think we should keep it, it's a rough guideline for how much a ship should be able to do. However, it's not an absolute rule, it's a guideline below which you are very likely not to be questioned, and above you might have to do some justification, but it isn't a hard bar to being approved. While we don't have many now, the time will come again when we have more litigious power-gamer type people do need to reject someone's doomboat idea and this gives us a good reason to look askance at it.
I would be in favor of changing the language in it to better fit the intention as a guideline rather than a hard rule.