newer iPod's will automatically apply, as default setting, sorting of Artists and Albums ignoring A, An and The if the Sort-Artist tag is empty
iPod Classic still requires an override in that tag for it to happen.
MB only saves the 'Artist Sort-Order' tag to the Library database - even if you have it set up as a Custom tag.
If you do have it defined as a custom tag, auto-complete will populate the field when selecting '...', allowing it to be manually saved.