Has used HTTPS since 2014 on all sites with domain that end .wordpress.com.
https://nakedsecurity.sophos.com/2016/04/12/https-for-everyone-wordpress-adds-encryption-for-all-customer-sites/
https://nakedsecurity.sophos.com/2016/04/12/https-for-everyone-wordpress-adds-encryption-for-all-customer-sites/