Let's actually check it:
Jagdpanzer 4 armor: 230
Su 85 penetration: 220-230-240
It has a 5% of probability to bounce a shot at max range. Even if someone would actually argue it is "a chance to bounce" with a straight face (that would be a showcase of utmost politician skills), IIRC percentages under 9 or 6 % are considered null by the game.
The rest is based on the wrong idea that jp4 can actually make use of its armor against anything bigger than a generalist.
Well, i mean IN the text you quoted i said that the su85 should lose some of its pen and even still, the fact that the pen on the su85 IS currently so high but, even as small as it is, has a chance to bounce the JP means that its armour is pretty impressive (i was under the impression that small chances to pen were null but any chance to bounce was untouched, as small as it is)
But, against the far more cancerous soviet TD (that being the su76) the JP armour and range really shines. Able to bounce 1 in 5 shells but also needing 6 pens to be killed vs guaranteed to pen and needing only 3 to kill and su76
And being able to bounce mediums more often than not IS a big deal when we are talking the prices were talking for these units.