Let’s not forget that if Bob transfers the domain to Alice then she can install whatever certificate she likes on the web server that will host this domain. Thus, she can remove Bob’s certificate and install her own. It doesn’t matter if Bob still has a technically valid certificate because the one that users will receive will be the one Alice installed. When the domain is transferred to Alice she will configure the domain’s registrar to direct users to the web server she owns through authoritative DNS records.