Template used for PDF linked in the email is different than the one used in admin links

Problem/Motivation

The PDF linked in the email sent to the customers use the commerce-invoice.html.twig template from the admin theme, but when you download a pdf from the admini interface like in /admin/commerce/invoices it uses the commerce-invoice.html.twig from frontend theme (only if it wasn't generated when an email was sent).
I don't understand the logic here

any idea ?

thank you