Hi team,
I've noticed that Experience Builder doesn't honour the Basemap Thumbnail Dimensions as they are in Portal.
They appear to be a square where as 64x64 (1:1) where as the Thumbnails on Portal are 3:2.

Are there any plans to make this a standard moving forward in AGOL and Portal? Or are there any plans to change ExB to honour standard thumbnail dimensions?
Put your best thumbnail forward (esri.com)
Cheers.