When I sent my intent to marry, I printed it and signed it. Because it happened during covid during the lockdown, my fiancee wrote it by hand, took a picture of it and sent it to me. I printed it as a big photo. It got approved.
You won't get denied because of it, but expect to receive an RFE. The date they're talking about is within 90 days after arriving in the US, so make sure you include that in your letter. Just say you're gonna get married within the 90 days, you don't need a specific date.