According to the documentation, the @name clause is added to the test string for EFI chainloaders.  This is based on os-prober outputting the same clause. 

os-prober output data seems to make the first field be either a device name, or a device name "@" chainloader path.  Unfortunately, the test for the presence of the @ reads:

    if [ x"${DEVICE#*@}" != x ] ; then

This tests for the presence of something after the "@", but is always true if there is no "@". 

I think the test should read:

    if [ x"${DEVICE#*@}" != x"${DEVICE}" ] ; then

It may be that a combined test (differentiating "A", "A@", and "A@B") may be needed, if os-prober has changed its output format.

This is line 124 of util/grub.d/30_os-prober.in in grub-2.06