There are certainly valid, conflicting opinions around signing/notarization requirements for software. But notarization does provide end users with some safety guarantees that legitimately make running the software less risky. The scariness of "are you sure you want to run this" prompts is fairly grounded in real risk assumed by the end user.
I don't know why this app would need Apple's signature in the first place, seeing as it's not distributed through the app store. Is this like how you need to pay for a certificate to make the "are you sure you want to run this" prompt look less scary?