The Regulations are substantively similar to those that apply in England, with the Coronavirus Act 2020 containing express provisions for each regional jurisdiction.
You are correct that there is no express mention in the Regulations to construction or building sites and so the restrictions and requirements stipulated would not apply to construction sites, except where, for instance, a workplace canteen formed part of the Site facilities.
The Regulations provide restrictions on movement and gatherings, although a valid reason to leave the place where you are living is to travel for the purposes of work, where that work cannot be undertaken at home.
The Regulatory 'physical distancing' requirements are mandatory in Scotland for certain business premises, as they are in Wales but not England, although these do not specifically apply to construction.
There are requirements within the Coronavirus Act 2020 for public health officers to make directions or instructions, which may relate to the isolation of a person who is potentially infectious, along with any related screening or testing requirements.
The Site Operating Procedures are not a 'change in law' although any compliance issues would almost certainly be determined by Health and Safety law. Consequently, 'physical distancing' may be considered a reasonable measure to comply with an assessment of risk to a person's health and welfare.
As you have already concluded, there isn't much within the legislation to assist with the effects of such measures, although as these are a change in law they would be a compensation event anyway, so it would be sensible to notify them as such. The effects can then be discussed with the Project Manager to determine what is actually 'due to the compensation event'.