Is it normal to require certain guest accessories?

Got invited to a college friend's wedding this fall. The attire is formal or black-tie optional. I got confirmation from the bride that tea-length or floor length dresses are good! However, she also wants guests to wear black. She specified no patterns on top of the black unless it's black on black or navy on black. The kicker for me is she also requested that guests wear navy or black shoes with black accessories (purses, shawls, etc). And my boyfriend who is invited needs to also wear a dark colored tie, luckily he already has a black suit.

I am not someone who has been to a ton of weddings in my life. I think I've been to 5 or 6 total and I'm almost 30. I've also never been to a wedding that was any more formal than cocktail attire. I was just wondering if this is normal? I'm feeling like I'm not even in the wedding party and I and my partner are having to purchase things specifically for the wedding and that frustrates me. My friend has very expensive taste so I'm also spending a decent amount of money on two nights in a hotel for the weekend and traveling about 6 hours to get there because it's in a state that neither of us (like not me, my bf, the bride, or any of our mutual friends) live in. But maybe I'm just an outlier for not having that stuff already?