One obvious reason the author doesn’t explore is that neither Wales nor Scotland has ever experienced mass immigration nor profound demographic changes in their population.
Scotland remains 92.87% white (2022), Wales 94.2% (2021), compared to England at 81% (2021).
In Scotland, 2.2% identity as Muslim, 0.4% as Hindu, 0.1% as Jewish.
In England, 6.7% identify as Muslim, 1.8% as Hindu, 0.5% as Jewish.
Scotland and Wales are therefore much more homogenous as populations. They’re whiter, less religious, and from similar backgrounds. They’re not as diverse as England is and therefore don’t have the challenges of community cohesion and social solidarity that England does.
It therefore doesn’t have the levels of intra- and inter-communal diversity which can provoke the kinds of tensions we’ve seen playing out in the streets of England over recent years, whether in Hindutva-Muslim ethnoreligious violence in Leicester or these anti-Islam and racist riots in recent weeks.
Scotland’s sense of its national identity has also not been challenged to the same extent as in England. Nor has a patriotic attitude towards Scottishness been derided as hateful, bigoted or xenophobic, as it has in England. (This sometimes leads to highly funny events, though, like when ScotNats try to claim they were victims of the British Empire.)