The dawproject import/export implementation in Cubase 15 Pro is exceptionally good, however I have observed problems with sustain (midi cc64) event export/import from Cubase 15 Pro (on both MacOS and Win11). I setup a simple test using only a single VST instrument track, recording a basic piano part with sustain pedal events (midi cc64). If I then export this project to dawproject and try to import again, whether it be an import back to Cubase 15 Pro, or another DAW like Bitwig Studio 5, I find that all of the sustain events (cc64) are completely missing. It appears that maybe Cubase is not exporting these events at all to the dawproject files.
When making much more involved test projects, I find that all of the other more complicated stuff, like midi and audio recordings, instrument and processing plugins and settings all get exported and imported completely fine (whether it be to another DAW or back into Cubase). Only the midi cc64 sustain events appear to be missing.
Ironically this seemingly trivial missing cc64 sustain data makes the dawproject format almost unusable for me in Cubase. It’s so close though 
And yes, there is actually a simple, but inconvenient workaround. I have found that for midi instrument tracks with missing cc64 sustain events in dawproject, you can individually export the tracks using plain old midi (.mid) files, and the sustain data is then properly exported and imported (no matter which DAW you import/export from, including Cubase)
Well, anyway, hope the Cubase dev team can eventually fix this issue. It is not a deal breaker for me, but it would definitely be a big help for my workflow, which involves moving data between Cubase and Bitwig.
Speaking of which, kudos to the dev team on Cubase 15, it’s absolutely fantastic, the best Cubase has ever been.