All of these emails are unique from the perspective of the social network but all will show up in your Gmail inbox.
This approach allows you to filter out everything sent to this address to a Gmail label or folder which can be useful for finding related emails in your inbox.
Just to be safe and not tip off the social networks; when you get the confirmation email for each new account, don’t click on confirmation link/button. Right click on the confirmation URL and copy the link. Then paste it in your browser to confirm your account.
Note of caution
Keep in mind, with every hack, there’s always a risk of getting caught by social networks.
If you don’t want to risk it then you will need to spend the time creating new email accounts for each social network account.