This is because AliExpress has changed their approach of assessing the quality of their sellers since the start of 2018. Therefore the rating of diamonds, crowns etc. has been taken away and been replaced with a little emblem against the sellers store name, identifying the store as 'Top Brand' (see Pic).
View attachment 2538
This makes searching for quality brand sellers more of a chore, as the plugin doesn't allow to filter on that.
If you import directly from Ali though, you can search for products by name and then select from the brands icons at top.
View attachment 2539
You still then need to go through the list to select the products you wish to import, while making sure the 'Top Brand' logo is shown.
View attachment 2540
This is slow and cumbersome new process and I hope that some of this 'fingerwork' can be automated through the plugin in the near future. But for now this is the approach I am taking, unless someone else has a better and quicker - but safe - solution to share.