No, that's not true at all. BUT, they are not easy engines to build. It's a twin cam conversion to a pushrod engine after all. There are a lot more joints that need to be lined up carefully and sealed correctly. Every one of them has been apart already, some multiple times. Then good lord only knows what's been done to them. Any unknown engine needs to be checked out meticulously as to condition and spec. Their main weakness is the short valve guides. There is only so much life in them and that decreases as the revs go up.
Considered against today's engines is a crude, nasty, old thing. Compared to engines in period it's an absolutely BRILLIANT piece of kit. World beating performance (literal and actual) for not much money. The only other British twin cam engine that can compare is the Aston six and that was an order of magnitude more expensive. World wide, only the Alfa four was comparable and, again, it wasn't as inexpensive, not inexpensively tuneable.