Hello,
when you convert from lossless to lossless there should be a warning when you add any kind processing. Such "You change the original audio track, are you sure?"
It is easy to oversee and easy to corrupt your library with it.
Applying a DSP isn't necessarily a bad practice in the way that lossy transcoding is. The program can't guess if that is what you really want to do. To avoid processing files accidentally during routine format conversions, save one or more presets that don't include DSP.
I'm sorry, I forgot that "decode postprocessing" exists. It defaults to on in the Converter, and with bit-depth as auto, the wordlength is reduced to 16, and there is no lossy warning when converting from DTS.
A better default for the WAV converter would be the postprocessing to off, and a message box with "do not show again" checkmark explaining how it works when it is enabled. Maybe they count on you knowing what you're doing if you install a 3rd party HDCD or DTS plugin.
Still, for now, you can create presets. And I would extract DTS and treat it like normal compressed file.
There is or isn't a lossy warning when converting from DTS. If DTS is in a WAV file, it depends on the container calling it "lossless", as it is encoded in PCM. If it's a .dts file, it will only have no warning if it is DTS HD MA, which is lossless.