The short answer is yes. If your event is public (ie anyone with the link can RSVP/register), guests will be able to make multiple submissions with the same email.
What happens when a guest tries to RSVP twice?
When a guest has already RSVPed to an event but needs to resend their RSVP using the same email address, the system will offer them two options. The first option is to edit an existing submission, while the second is to create a new submission entirely.
If they choose to edit their existing submission, the system will overwrite the previous one with new information. However, if they choose to create a new one, the data previously sent will remain unchanged.
What happens when a guest tries to RSVP twice (ticketed event)?
The same thing happens if the person has RSVPed to a ticketed event and then tried to repeat the process using the same email address. The guest has an opportunity to either edit their previous RSVP or create a new submission entirely. A notable difference is the cases when the event has an invite list. In such cases, there is no option to create a new submission, and the invitee can only edit the submission they submitted previously.
Since there is no option to create a new submission if the event has an invite list, the data from the first RSVP will be overwritten in favor of the edits made during the second.