Sorry 1x, 2x,3x is a resolution of same artboard. We cannot set 375 in 1x as per requirement.
For more help please check out the link https://helpx.adobe.com/in/xd/help/export-design-assets.html
So, as a result, do I have to work with 3x to export to 3x size?
On the basis what resolution you want, you can choose 3x, 2x, 1x.
As shown in the image attached above, 3x, I exported the PNG to 3x.
I exported a work with a size of 375 by 3X, but it was exported with a size of 375. The desired size is 1125px.
Please Go to the link:- https://helpx.adobe.com/in/xd/help/export-design-assets.html
It will help you for better understanding on how export work.
For Ex you have artboard size 90*90 if you are exporting :-
1X size will be 90*90 , in 2x size will be double and in 3x it will be triple
if you exported in 3x in 3x size will be 90*90 and in 2x it will be half and in 1x it will be 1/3.
Hope it will help.
I was wrongly understanding that the current artboard is a single export option, not an option to set it to 1x.
I finally understood.
Not only 3x was exported, but 1x, 2x, and 3x were all exported, but I couldn't catch it.