Printing issue - wmts webp image format

Hi there

I'm using a wmts layer as a basemap in my application. this wmts provide 3 different formats of image webp, png, and jpeg. to achieve maximum performance I decided to use webp format. but once I change the wmts image format to webp, it didn't come up in the output of the print or even export tool.

it works fine with jpeg and png and wondering what would be the issue with webp format.

Viewer version: 2.11.1.1543

Essential version: 4.10.3.23