How many people might be affected by this? It is hard to say, as the pandemic led to changes in work, and also to changes in where people were living. A constraint was that the housing market was not operating at its full capacity for parts of lockdown, and the markets in England and Wales and in Scotland operate under different regulatory environments.
However, the 2011 Special Workplace Statistics singapore rcs data (SWS) and Special Migration Statistics (SMS) allow us to look at what was happening a decade ago. Both datasets are available through the UK Data Service
Using the SMS, we can look at migration flows from specific origins to specific destinations. we find that in the year prior to the 2011 Census, 40,975 people moved to Scotland from the rest of the UK, and 42,554 moved from Scotland to the rest of the UK (these compare to around 490,000 moving within Scotland).
The totals in each direction are not hugely different, but it remains the case that the effects are opposite: those moving to Scotland would appear twice, and those moving from Scotland would not appear at all. However we can distinguish here between individuals, and their contribution to an aggregate total.