Exporting to csv Mongo collection with arrays

I’m exporting to csv a collection subset with Compass 1.39.3 and I run into the follow problem: when the field is an array, I get as many columns as the number of possible elements in the array.
Example for the following collection:

{"arr":[{"val": 8}]},
{"arr":[{"val": 3}, {"val": 5}]}

I get:

arr.val[0]	arr.val[1]
8		NaN
3		5

It seems to be a change in the behaviour of Compass: I updated it recently and so far I was getting 1 single column containing the arrays in JSON format for every document, i.e.:

[{"val": 8}]
[{"val": 3}, {"val": 5}]

Why is that?