On par means similar performance, not carbon copy.
You're right. In English, "on par" factually means equal footing or same playing field with similar attributes. It does not mean a carbon copy. The term comes from sports, when two teams or two players are facing each other, and they both are considered to have similar chances to succeed, despite being different from each other, even if one of them has some kind of superiority or malus over the other, then they are "on par". Source: Englishman here, oi! So, the sentence to give Shocks a better grenade so that they're in the same playing field as other units' nades is valid and contextually correct.
Let's not focus on patch notes sentences. That's nitpicking for the sake of nitpicking schematics. We should Focus on the data that Hannibal presented earlier in the thread.
I also do not think that arguments should rely on sentences of patch notes which were most likely written as the very last thing before releasing the patch. We could argue that the grenade should be on-par only with other specialist anti-infantry units, and any infantry which is not a specialist anti-infantry unit, so a generalist and whichever infantry which has the potential for AT upgrades (not via drops) should be taken out of the equation of the term "on par". That's a can of worms there.
It's better to focus on units in their context, and not plain 1:1 data comparison.