Is it possible to pull data in ADB sideload mode
I know this is a very old question but as there is no answer I post this one.

Just had a similar problem. Look at this:
https://www.howtogeek.com/240655/how-to-copy-twrp-android-backups-to-your-pc-for-safe-keeping/

remember to take out the "Enable MTP" option in the "Mount" Section of TWRP.

Edit: Just re-read your question, I guess you didn't have TWRP installed. Not sure how to solve your original issue. In case you have TWRP installed or manage to somehow do so then my answer still stands