What the heck is an 8bit codec in Premiere?

Premiere doesn't have quite the same export options setup as Resolve. Including for setting specific bit-depths.

Within Premiere's processing pipelines, media is handled from the original metadata in the project panel through the sequence to export. All media on a sequence is handled by Premiere in the bit-depth it is in (there's no sequence bit-depth) and all media is processed in 32 bit float unless you apply an old 8-bit color/tonal effect, at which point it drops your processing into 8 bit.

At export, you select a format/codec and Premiere simply uses the bit-depth of that format/codec combination, taking the 32-bit float it's been working the media in to the bit-depth of the export. Some format/codecs are by the standard of that format/codec specific bit depths, many can hold variuos bit depths. Most ProRes for example can be up to 10 bit, some 12 or higher.

So you don't specify the bit-depth on export. Use the preferred format/codec that you wish for the deliverable needed.

And ... I am a contributing author for a pro colorist teaching subscription website, where most members are based in Resolve though many work in Avid, Baselight, or even Mistika. And from much association with that crowd ... I found his comment somewhat ... odd. I don't understand why he gave that instruction.

Neil

using mediainfo 

https://mediaarea.net/en/MediaInfo/Download

please tell us the specs of your source clip. In particular the codec

if you hover your mouse over the video section, you'll see a list of all the info.  If you can post a screen grab, that would be ideal.  I

why are you trying to do this?  if you're trying to deliver to a certain specification, please give us more detail.