But that is down to the electoral system - in terms of constituency seats, which is the equivalent of the Westminster system, the SNP won 85% of the constituency contests.
Wrong. In the Scottish Parliament which is the parliament of the government of Scotland, the SNP won 62 constituency seats which is roughly 48%.
But in terms of whether one party dominates a defined geographical area (or a 'state') then it is perfectly relevant to ask the question about how many seats a particular party wins in that geographic area even in a contest that covers a wider area. So looking at the SNPs results in Scottish Westminster seats seems entirely relevant. Indeed didn't Sturgeon herself claim that SNP victory in Scottish Westminster seats provided a mandate for a referendum and the Scottish vote for remain to provide a mandate in Scotland against brexit.
It's fair to argue that the SNP dominates the Scottish seats in the UK parliament but there are two problems with the way you are trying t interpret that. The first is that the phrase "one party state" does not mean "one party dominates a small part of the state". It means the party in government is the
only party, or, more broadly, if there are other parties, none of them have any prospect of gaining power.
The second problem is that you are ignoring the electoral system in place in the UK. You can win all the seats with only 50.1% of the votes if they are evenly distributed over all the constituencies. However, in that case, you could go from all the seats to none of the seats at a general election with only a 0.100001% swing. The SNP having nearly all the seats in Westminster is not a reflection of its dominant support so much as how its support is distributed.