No, not really. They've been getting thicker and heavier since iPhone 6 Plus was bending in people's pockets, because I'm not sure if you remember, but after Jobs died they made iPhone 5/5s which were thinner than 4s AND THEN 6 and 6 Plus which were even thinner, if not the thinnest ever.Since then, iPhones have been getting thicker and heavier for each generation, what with all the glass backs and new internals they've been piling on. The 12 Max is a half-pound behemoth just like the 11 Max, both weighing in at 54 grams more than the first phablet iPhone (6 Plus).
After the bendgate they pretty much stopped bragging about that and changed internal construction of iPhone 6s. But that wasn't enough - it still had pretty small battery, so with 7 and 7 Plus they made it (if I remember correctly) last 1 hour longer. Next huge increase in battery life came with 11 and 11 Pros, but they are also the thickest iPhones since iPhone 4.
Let's compare the depth of the newest devices:
So yeah, I stand with what I said earlier. iPhone 12 Mini / 12 / 12 Pro / 12 Max (they all have the same depth) are thinner than iPhone 5S. Batteries on 12/Pro/Pro Max are smaller than on their predecessors. *sigh*