This is how HOME behaves when there is no original SV data for it to fetch the tera data for.
I can add some "rejuvenation" for the conversion logic to detect what the legal values would have originally been.
edit: added
https://github.com/kwsch/PKHeX/commit/b212ef42b508e86ea988771d159fbb619b88d6ac
You don't need converters to convert from DSeSume,DSeSume can convert for you,follow these steps :
Open > DSeSume > Click File > Open Rom > Select your rom > Wait until the rom has been loaded > Click File > Export Backup Memory >Save as : b-pokemonb.SAV(Pokemon Black Example) > Transfer it to your NDS.
Worked for me.