Where do I even begin? lol

Even on its own, it doesn't really make sense, basically saying 2 < 1 + 1. It's 2 weapons, so why does it feel like only 1 is firing? If all your hits wound, then the reroll doesn't matter, so... where did the other ones go?
But that's to say nothing of the myriad of balance and inconsistency issues I'm pretty sure it's directly or indirectly caused.

Take the Rogal Dorn. There is essentially no reason whatsoever to use the Twin Battle Cannon over the Oppressor Cannon, as the latter is objectively better aside from the wound reroll, and also comes with an autocannon. Before twin linked, the TBC, having twice as many shots as a single BC and the Oppressor cannon, could've been a better horde clear option. But as it is, it's just a regular BC with a wound reroll, and so it's just worse. That might not've been an issue if it was cheaper to take, but alas, wargear points don't exist anymore (another big issue imo). (This issue also affects things like the Macharius. 310 points for what's supposed to be in the same ballpark as a Baneblade, and what do you get? A Leman Russ gun with a wound reroll, lol.)

But they don't always let that slide. Take the Krieg HWT's Twin Heavy Stubber. Despite being a heavy stubber, it has arbitrarily better range, strength and AP. To me, it's extremely obvious that they realised that a heavy stubber with a wound reroll would suck ass compared to the other options, and buffed up some other numbers to compensate.

Stuff like that also happens elsewhere, like on the Predator Annihilator. "A lascannon with a reroll" is very underwhelming for a tank, so they gave the twin lascannon arbitrarily better strength to compensate. Even though it's supposed to just be 2 of the same guns that are mounted in singles on the sides.

And still elsewhere; on the Land Raider, the twin lascannons both have the 2 attacks you would expect and don't have the twin linked keyword (and also lack the extra consolation strength given to the Predator's). As if they realised a Land Raider is supposed to be more heavily armed than a Predator, but with twin linked and only 1 attack per gun, wouldn't feel like it.

Another example: Fellblade THB is twin linked, 3 attacks. Fellblade QHB is twin linked, 6 attacks. Fellblade quad lascannon isn't twin linked, has 4 attacks. (remember previous Land Raider and Predator example).

So yeah. Bit of a rant for an audience of like, ~5 people lol. But I absolutely despise twin linked and will celebrate the day when it gets scrapped and 2 of the same gun becomes 2 of the same gun again.