The point is that the government is obviously finding ways to avoid a referendum because they obviously don't want Scottish independence.
Let's not be naive here.
The hard truth is that governments of any country on Earth favour self-determination in two cases: (1) when it does not apply to them, and (2) when they expect that they result will favour their interests. That's how geopolitics works. "People's interests" is just for PR.
How often does a country need to have a referendum on independence of regions that are so inclined to be said to support self determination? Also the polls leading up to 2014 were close enough that the result wasn't certain, yet the government went ahead.
I never said the UK would be happy with Scottish Independence. But if Independence was the clear preference of the people, the UK would let them go. The same can be said for the US and Puerto Rico, but not for China.
You said their position was "not to allow", which makes it sound like the Scottish people clearly want one but the UK won't allow it. That is not the case.