The DNG files DxO PhotoLab 3 created are only meant to be used as intermediate files for further processing in other applications. Additionally, some corrections have been applied in a non-reversible fashion, such as demosaicing, noise reduction, etc.
DNG files created by DxO PhotoLab 3 are not equivalent to the original RAW files, and for this reason, you should not consider DxO PhotoLab 3 as a DNG converter. It only makes sense to produce DNG files with DxO PhotoLab 3 if you wish to use these files in another program other than DxO PhotoLab 3.
If you want to return and continue working on an image you exported from DxO PhotoLab 3, we strongly recommend that you use the original RAW file and its .dop (sidecar) file, which remembers the initial settings you used to process the image.