It's the desired and documented behavior https://www.limesurvey.org/manual/Participant_settings/en#Enable_token-based_response_persistence

Expected result

Start a new response because only completed response are valid.

@tibor.pacalat : there are NO issue here

If the survey is anonymous or "Enable token-based response persistence" is set to "No", this will add a new response.

From manual : https://www.limesurvey.org/manual/Participant_settings/en#Allow_multiple_responses_or_update_responses_with_one_token

If the survey is anonymous or "Enable token-based response persistence" is set to "No", this will add a new response.

This is the expected when Allow Multiple Responses = on

What about when it is Off?
I guess it shouldn't add new responses.

If it's ON : reloads the last response

Off or No : this will add a new response if token was not set as submitted.
On or Yes : reload existing response if token was not set as submitted.

Allow Multiple Responses is only here fir SUBMITTED/COMPLETED response. There is no other purpose !

Allow Multiple Responses is only here fir SUBMITTED/COMPLETED response.

Well, it doesn't says so specifically.. and not sure if we should limit to that specifically.
Don't think people expect that.

If you don't allow multiple responses, why you would allow multiple incomplete responses?

Don't think people expect that.

Some people expect that

If you don't allow multiple responses, why you would allow multiple incomplete responses?

You really think people find email, send email to have a bunch of partial response stop at step 1 when there are 24 steps ?