It would seem that way, and might be obvious if it were one team working on both features. However, there is probably multiple teams involved, politics, workloads etc.
Correct. I generate a new email "mask" for each website, yeah. I can choose for a random one that looks like something like 8*kshaj*@mozmail.com so that it provides an extra layer of anonymity, or I can choose my own that would look like facebook@*myuser*.mozmail.com.
The Firefox Relay app tracks all the email addresses, and which websites they were generated on, so you always know what you signed up using. Seperatly, I also use a password manager to automatically generate and save long and secure passwords.