I'd argue it's more about DF being light on systems rather than light on content. Less systems means less stuff that everything has to be built around, leading to more room to just work on content & related items. If the devs didn't have to completely work everything around covenants (stories, class balancing, abilities, gear sets, quest chains, etc), I imagine SL might have had more to do overall or at the very least quicker content releases.
I still think DF will be relatively light on content overall, but that IMO is more to try to get this expansion & the next one out quicker & with more of a steady cadence than SL had. If the content feels light overall while continuously coming out & fixing bugs/design flaws as they go, I think it'll overall be one of the better received expansions.