Thurstan (Toustain) de Montfort-sur-Risle (de Bastembourg), Seigneur de Briquebec - Question regarding currently linked parentage ...

In the instance of these early Normans, the curator has done an excellent job and the Curator's Notes and Overviews give the documented information and the traditions, since the information for the early Normans is sparse. You can message the curator on Geni.

Thank you, Hatte. I'm newish to Geni and simply researching my family history, so not a professional anything.

I curated some of these profiles early on, but the current curator has a much better grasp of the sources.

You could go either way, stop at Thurstan or go to Ansfrid, since it's a tradition, albeit without reliable primary sources. Just be aware that early Medieval will not have the primary sources or the reliability of later and the best Geni solution is often to give several alternative accounts.