Could you please check the page saving function on aliexpress item pages?
It doesn't save most of the page content.
aliexpress (dot) com/item/32954659056.html for example.
Save and scroll down to compare the source and saved page.

Update:
It seems I found the reason of this behavior - a lazy load of the item description in the middle part of the Aliexpress page.
I'm on 1080 notebook screen (and thats quite typical resolution for portable PC) so the page reports "all done" to the browser while the main page part is not loaded until I scroll down below the first screen.

Anyway the SingleFile Firefox add-on is not affected by the lazy loaded content and saves a whole page with no pre-scrolling required.