Have you been able to successfully accomplish this with any other Gutenberg block? Blocks are developed primarily in JS, and the code you are using to retrieve the custom field is in PHP. That’s great if it works, I’ve just never tested it, and didn’t know if it was possible.
Anyway, here are the field names for the various elements of the Profile Block:
title
subtitle
bio
mediaID
mediaURL
facebookURL
twitterURL
instagramURL
linkedURL
emailAddress
Again, I’m not sure what you’re trying to accomplish is possible. The attributes for those fields are defined in greater detail within the previously provided link.
Thanks!