Maybe a descendant was working up that line, went out on errands, got caught up in daily tasks and forgot. On what date was the profile created? Can you see if there are recent edits or sources added? Is there a profile manager for the profile of person whose parents have yet to be acknowledged?
I'm trying to summarize what I know of the family group in a research note or comment on the profiles I'm creating, but my priority is posting the source data as well as I can, so that someone else can pick up building the family where I left off, or more easily confirm their connection-just in case something happens with me.
Some people and locations are known to have been plagued by published errors that persist in being reproduced. There's a lot of that in my tree but I have learned many of the trouble spots from past research and a dozen years on ancestry.com. I've noted several of these cases on ancestry, and in my personal notes. In those cases, I do a lot of searching around wikitree scouting out the existing profiles several generations back, beating the bushes back and forth and out from the children, to take notes on all the connections that should be made between existing profiles. That takes time! I'm working this process now with the Hall family in Medford, MA, where it seems there are errors in a widely distributed town history. It will be necessary for me to find a very patient, experienced Wikitree genealogist who is willing to look over what I have found and to collaborate with me. In this case, I know the version published in the history of Medford was called into question a long time ago in the NEHGS Register by W.H.W., who I assume is William Henry Whittemore, and it bears investigation.