I agree with you. This author is sketchy.
I struggled with doubts in the past and asked God for a sign and He gave it to me. The problem was that my doubt wasn’t a result of lack of proof but from my own unwillingness to believe and trust in God.
As simple as it seems the way my doubts were resolved simply by trusting God the best I could, not from a sign.
"Trust in the Lord with all your heart and lean not on your own understanding, in all your ways acknowledge Him and He will direct your paths." Prov. 3:5-6