CE Update 12: Odd behavior between DWG version and AEC Objects version for Civil 3D files

This is an update to an older thread about working with Civil 3D files

https://communities.bentley.com/products/interoperability/f/fileformats-forum/133557/civil-3d-2017-objects-not-backwards-compatible-with-earlier-versions

I have an older Civil 3D file created in Civil 3D 2009. Opening the file in MSCE Update 12 I am given the choice to upgrade the DWG AEC objects to the current version (Civil 3D 2018) or open read-only. When opening and upgrading I would expect that the entire drawing file would be upgraded to the latest version, but that is not the case.

Saving this drawing the base dwg file format is still DWG2007, but the AEC Objects stored in the file are in 2018 format. Opening the drawing in Civil 3D 2016 the base graphics display fine, but the AEC Objects are drawn as proxy graphics as they are a newer format. Only when I open the file in Civil 3D 2018 and save it is everything in the file at the same version.

I did a SaveAs in MSCE Update 12 and saved it as a 2010 format file. Again the DWG was created as 2010, but the AEC Objects remained at 2018.

This is really messed up.

It would be nice to have another option on the MS_OPENDWGAEC variable to automatically upgrade the DWG version to the AEC Objects version so you don't end up with these mis-matched formats. Setting this variable would not allow the user to save this to any DWG format other than the one that matches the AEC Objects.

I'm guessing that since you have the alert dialog you (Bentley) do not have the ability to save the AEC Objects to earlier versions, which would be the option we would really like to have.