[skissane]

Yes, but the UK has evolved a lot since 1973.

In 1973, the UK was much closer to a pure unitary state – there was no Scottish Parliament, no Welsh Parliament; the existing devolution in Northern Ireland (the Parliament of Northern Ireland) had just been abolished the previous year and the attempts to reinstate it in 1974 and 1982 proved to be short-lived failures. By 2016 there was a devolved Scottish Parliament, a devolved Welsh Assembly (designated a Parliament in 2020), and a devolved Northern Ireland assembly.

I think the evolution of devolution (pardon the pun) is a recognition that the UK needed stronger protections for Scottish/Welsh/Northern Irish rights against the English supermajority, and a "double majority" for constitutional-level national referendums would be a step further in that direction.