pCloud support replied and confirmed:
"Hello,
Thanks for your e-mail.
The European servers can not return MD5 because it's not supported. They are using only SHA1 and SHA256.
Should you require any further assistance, do not hesitate to contact us!
Regards,
George Lewis,
pCloud Tech Support"
I replied asking them to update the documentation.
Anyway please consider whether with the confirmation, this should be integrated in the official rclone branch. And once again thank you for following this up.