Not anything yet I'd find offensive. I have had location issues before with people expecting me to drive several hours to sell them birds before.
Delivery as in through the mail? Or to have them dropped off? Still wouldn’t consider it a rude question though, how else are you supposed to know when to expect birds to be arriving? What if you were still building a pen for them or moving along your own extras to make room?
Someone upset at being asked if they're certified is a warning in my opinion. If they're not, then just say so and move on. To get upset makes me think they're hiding something. Though, to go past state lines, they do have to have NPIP paper work to go with the birds
The invoice would catch me off guard, but I'd be more than okay to print one up if requested. As for photos, when I sold birds, I would run out and grab some for people that wanted to see what I had while inquiring if I didn't already have images of those birds. People that are proud of their flock offerings aren't going to be unwilling and snotty about showing images
Delivery as in mail, they told me what the cost of shipping was but hadn't specified what service they use or which speed they'd use by default, and I've learned not to assume people shipping living beings will always default to express. Plants and animals take the same care for consideration to me
I was indeed asking, and said as much, because i needed to be sure their enclosure would be finished in time, I'd shared photos of the construction with them. I need to build the roof, lid, and then fence in and reinforce the sides and it's ready for installation! Plan to build a much larger aviary around it if we stay with keeping quail after our first covey experience.
Yeah the NPIP thing really wigged me out and was my first big red flag i noticed. I've since learned that i can ask for an NPIP number so i can verify the registry is valid and legitimate. i think if i had gone through all the effort for applying to the program, I'd be very eager to share the certification with anyone who wanted to see the result of those efforts!

someone shared a link to the place you can look registrations up by state, which was super helpful.
Also, that makes total sense but i didn't actually know that yet about needing NPIP papers to cross the state lines (which yes they would have been shipping them across state lines). That was a question i had intended to ask this seller before the conversation tone changed.
Re; The invoice request -- it wasn't for a paper copy, but rather for them to email me the PayPal money request so i could make sure payment was going to the correct person. I typoed the username for a direct money send request once years ago and it really sucked, though fortunately was not a huge amount

so i always have a seller send me the link to their seller page and pay them directly, or email me an invoice i then pay.
If i really truly have to pay by typing in their username by golly i can suffer quadruple checking i did it right, but i made my preference known.