They cant hold payment if you require immediate payment.
Ebay has become a mess, It's actually harder to combine shipping. I'm not even sure how to do it anymore and i've been a seller on ebay for over 20 years. It used to be an option on the listing, then it was an option in your store settings and then it just disappeared. I did just sell 2 items to the same buyer today and the label printed from one order, but I didn't look to see if Ebay combined the shipping or charged them double....
My ebay page is just a giant advertisement for my website now, so I really don't care. I even say on all my listings all records are cheaper on the website. If they're smart enough to find the website they will save a ton on money. Few do, though, I'm afraid.