I think when people talk about lock-in in Roam they refer to how usable those files are outside of roam. I only used roam very briefly sometime in June (…could be, pandemic time is weird?). To this day I keep finding files that I need to clean up with block-references or custom-syntax or worst case delete, because they’re unusable (I don’t know where those links lead!). They are fewer each day, but they show up here and there.
Would be great if you could help out some folks with some answers to this: How to import Roam backup into Obsidian while preserving block-level references/links?. I wasn’t around when those “high-fidelity” exports were created, but based on the threads I’ve found here they are meant to be re-imported into roam as backups, not really to be used by other apps.
Edit: Changed the link to the original question. The request to the plugin is here: Import Roam backups in JSON or EDN format, so that block-level links/references are preserved