Error while importing Activities file in V5.3.2, which is exported from version 5.3.1

Here is the issue I am facing:
(1) I was using version 5.3.1 and had created WBS, consisting of Activities and Milestones. They are logically linked to each other.
(2) When I create a new instance of version 5.3.2, I want to replicate the WBS created in earlier version.
(3) So I export the Activities & Milestones from 5.3.1 and then import it into 5.3.2 --- I get multiple errors.

Please refer the screenshot. The error says: Project/ Responsible is mandatory. However, in all line items, there is a valid project and responsible person mentioned. Yes, it is very much present there. I am not sure why the import facility is not able to recognize it. I have not made any changes to the exported csv file.

One observation: I noticed that while exporting, a few fields are selected by default. I can obviously select/ deselect all. However, while importing, the tool shows a list of fields that it expects -- but this list does not match with the pre-selected list during exporting. I think, the list of fields selected during exporting (by default?) should be the same as the list of fields expected during importing. Am I right?

Oops. I figured it out myself... In 5.3.2, I did not create the Project, and was trying to import activities directly. Hence the tool was throwing the error. After I created the project, I (re)imported the data and it accepted!! Voila....

I am still curious to know about this, though:
I noticed that while exporting, a few fields are selected by default. I can obviously select/ deselect all. However, while importing, the tool shows a list of fields that it expects -- but this list does not match with the pre-selected list during exporting. I think, the list of fields selected during exporting (by default?) should be the same as the list of fields expected during importing. Am I right?