What that first link claimed was "By 1965, large-scale power plants were being sold commercially at costs competitive with fossil fuel plants."
And I explained why that was misleading. They were being sold at a loss. The PRICE was competitive with coal, but the cost was not. This was even before changes in regulations.
The Turnkey Era in Nuclear Power, H. Stuart Burness, W. David Montgomery and James P. Quirk, Land Economics Vol. 56, No. 2 (May, 1980) (available through JSTOR)
The latter is interesting, as it also gives an explanation for why utilities might have liked non-turnkey contracts: any escalation of capital cost can be (and very often was) passed on to ratepayers. In light of this, what really nailed the first US nuclear age was the passage in 1978 of PURPA, particularly the part about non-utility suppliers.
The key point here is the perverse incentives of regulated monopolies. If the monopoly can get the regulators to agree, then the more capital intensive something is, the more money the utility makes. They do not have an incentive to keep costs down.
And I explained why that was misleading. They were being sold at a loss. The PRICE was competitive with coal, but the cost was not. This was even before changes in regulations.