Here is a screen capture of the Creo file it is saving as even though .ai format has been selected:
https://shared-assets.adobe.com/link/c5a366b2-c7c3-4c6d-7322-01a560badbf8

It takes saving twice (see links to 6 steps0 to finally get an .ai file:
Step 1 - https://shared-assets.adobe.com/link/d2668e83-b384-4887-412c-c9cd1c090a91
Step 2 – https://shared-assets.adobe.com/link/71e19fb9-6b6a-49da-71d9-1893af67c17b
Step 3 – https://shared-assets.adobe.com/link/d33ad57c-e020-4381-5b89-a0231c6bad01
Step 4 - https://shared-assets.adobe.com/link/e6847fef-7c38-401a-5532-7d1e9dbb717e
Step 5 - https://shared-assets.adobe.com/link/aab87d77-152f-4238-6433-72bace2d17c2
Step 6 - https://shared-assets.adobe.com/link/87f69c8c-b7f3-46b5-5ed9-84edff63fad3

Then only way I can get an .ai the first time is to save it as an older version - CS6 : https://shared-assets.adobe.com/link/de7a7f35-444a-4bc0-4686-b7b9964437b7

See Mohammed who I IMed with regarding this issue 12/10/20