Report want PNG Cache - BUT .PNG SHOULD NOT BE DONE WITH CACHE

Web Performance Discuss Test Results
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Web page performance test result for

According to various Internet comments, .PNG SHOULD NOT BE DONE WITH CACHE
For example:

You should not gzip/deflate PNG images!

Is webpagetest.org Report wrong ?

Leverage browser caching of static assets: 27/100 Learn More

FAILED - ( No max-age or expires ) - https://www.ankauf-diamanten.de/juwelier-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-diamanten.de/juwelier-home.png
FAILED - ( No max-age or expires ) - https://www.ankauf-diamanten.de/top.png
FAILED - ( No max-age or expires ) - https://www.ankauf-diamanten.de/down.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/schmuck-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/gold-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-schmuck-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-diamant-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/diamanten-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-gold-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/zahngold-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-zahngold-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/platin-ankauf-industrie.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-platin-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/uhren-ankauf.png
FAILED - ( No max-age or expires ) - https://www.ankauf-24.de/ankauf-uhren-ankauf.png

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gzip/deflate is compression and different from caching. If those images are not changing regularly, they should absolutely be cached with cache-control headers.