The max-height is read from the browser using a Element.scrollHeight. It is compatible on all browsers (so also Safari)
The Element.scrollHeight read-only property is a measurement of the height of an element's content, including content not visible on the screen due to overflow.
So this should work on Safari as well.
When looking at the URL you gave me, I can see that in the about text is an image that is lazy loaded. So maybe that is the source for this behavior on Safari. Because the image is not loaded when the scrollHeight is taken, it is not in the equation?
Could you try to turn off lazy loading and see if this is indeed the root cause?
In the mean time I am trying to get my hands on Safari (not a Mac fan myself )
Small update: was able to get my hands on a developers VM with windows 10 and Edge, installed Safari (last version that is supported on Windows).
Now when visiting your test site i get the 'Safari can't open the page because can't establish a secure connection to the server' message... So that is a dead-end.
If you could try disabling lazy load and / or remove the image entirely from the about text: just to pinpoint the root cause. If this is related to that image / lazyload, then we have something to work on