Yes. There's no way for Marketo to know this record represents the same lead (remember, email address is not actually a unique identifier, merely a primary dedupe key for some entry points into the system).
This is why we always recommend not doing this.
As soon as a lead is created in Marketo, push it to SFDC and assign it to a lead queue, until it's ready for sales, inside sales or telemarketing assignment. Lead queues offer a very flexible mechanism in SFDC to store leads and more or less hide them from the sales.