Yes that’s accurate for uAsset files, but you can upgrade a project that contains them and the migration utility will attempt to make them work depending on the asset type. For smaller version jumps, this is usually relatively possible. For larger version jumps, this is very prone to breaking the asset.
If it’s an art asset mostly, I’d export the pieces from the old version to generic files then reimport and rebuild. If this is a code/BP asset, you can try forward migration but very old files will be tough.