You can request airline to issue a certificate of cancellation. If cx, they have a link in webpage to do it. It takes 1-2 weeks. Last time I could claim and got the confirmation from insurance company before I receive the certificate.
Think it is case by case. My case is "well known" case, T8 in hk.
No harm to apply now even u have submitted the claim. In case they require, you can give them immediately.