Complete bunk, pay them no mind.
A winch is like a sink drain, your battery is the sink, and your alternator is the water tap. When you remove the drain (start the winch), it'll drain the water in the sink (battery), so you need something to fill it with (alternator). If the drain is faster than the tap, then it'll eventually run out. If you stop and let the sink refill occasionally, you'll keep the sink full. Now, most people upgrade their tap (alternator) so they can leave the drain open and the water level won't go down.
I have run my winch off the 42A alternator with no problem, no damage, but I do bump it to 2,500 rpm's to give the faucet a little more juice.
I have a Ramsey, bought it used, and it's been an awesome winch. I have seen both winches fail, Warn and Ramsey, so it depends on how it's been taken care of that matters.
Bill, let's hook up, me and my POS REP 8000 and your Warn 5000, we'll see which one gets the job done. I too have seen many 5,000 and 6,000 lb winches just stall out, nothing left, so they're not large enough, even for a Zuk. If you think they are, then go ahead and use them, just remember me when it stalls out. They may work well most of the time, but when you need larger and don't have it, you might as well not have bought it.
I have also seen 8,000 lb winches stall out, but there was a LOT of heavy mud. The pic below shows the winch I bought (this used to be my jeep), and this was the only day I'd ever seen it stall out. Another 8,000 lb winch was hooked to it to get it out.
Winter Harbor, Maine
'81 CJ-8 Scrambled, It's a Jeep, Chevy, IHC kinda thing!
'88.5 Zuki, 7" Lift, Locked, Swamped, Rolled, and just generally broken in right!