No group rendered in Commerce product display

Hello and first thanks for this useful module,

using Drupal Commerce and product displays,
i would like to group 3 CCK text fields in a group (horizontal tabs).

Usually easy with field_group module ;) !
But on product displays, with groups defined in the "manage display" tab, groups are not rendered (no markup rendered, fields are displayed normally).

Don't really know if it is a Fieldgroup issue, an Inline Entity Form issue or else...

In a node (article or else) groups are OK.

If anyone else solved this issue or if any expert has any clue ?

i have tried version from 1.1 to 1.3 (even 2.x), updated all other modules, can't figure how to achieve this...

Thanks !