Cannot be a crossover as NGC will only cross PCGS holdered coins anymore, all others have to be cracked by the submitter or at NGC and submitted raw.
Nobody is frowning on you but you very likely lost a fair bit of value by cracking that slab, most of the value of that coin in that grade was the slab which is very desirable to slab collectors. As you have discovered NGC does not recognize that VAM, They only recognize the top 100 and maybe a couple of others. Your only recourse now if you really want that VAM on the label is to spend more money on a coin that you have already put a lot of money into by sending to one of the other two services. Myself I'd just get a small round sticker, write VAM-4 on it slap it on the slab and call it good.