True.
It's one of the inherent weaknesses of the system how the armour being capped, or nearly so, seems to be the best choice most of the time.
While a lot of weapons, back in the day, seem to be poorly balanced, the construction rules are based on them; Max armour is an actual choice when you could get a third more burst firepower instead by installing an extra medium laser and a heatsink.
We now sit on a mountain of legacy, and have to make do with what is.
Still, I think it's odd that clan beam weapons get such significant gains (2/3s more range, aka ~+25% over IS equiv., +2 damage, less weight and crits if possible, the PPC has +50% dmg...) and missiles weight half, with potential gains in (minimum) range, and ballistic weapons, on average, just seem to weight 20% less, and maybe save a crit.
Well, a Gauss Rifle has to be balanced against other similar options, and I think it does an ok job against, say, ER PPCs, while on the IS side it is a shining example of former lostech still towering over the alternatives - just like the LBX 10. But the latter, on the clan side, isn't quite as impressive. I actually think the 5 may be a better choice, what with it weighing less and having the same damage per ton.
I assume the designers just didn't want a 9.5 ton weapon - because 9 would be a bit low compared to the 5.
Edit for word mixup.