This policy was dropped temporarily for the Scottish Parliament elections but is now back and being advertised on TV with a deadline of February 2022.
I would have thought there was zero chance, even if everyone could easily afford it, that there are enough electricians in Scotland to fit wired alarms in half the 2.6 million homes in Scotland by 2022.
Speaking personally, we have 5 WiFi linked battery smoke alarms, plus a wired alarm, plus three carbon monoxide detectors (one for each gas appliance.)
They don't meet the standard because the battery alarms are not sealed, even though they're a "smart" type that let you know in multiple annoying ways that the batteries need replacing. They also enforce an automatic ten-year service life limit and use very long-life batteries. In some ways, they exceed the standard**, but to meet it, we'll have to scrap them and get an electrician to install new wiring.
I think someone has "got at" the Scottish government over this and to a degree they've specified the technology, not the requirement.
Never a good idea to have the government specifying technology, but the prime problem with this is many with limited resources will say "£300-£1000 on new smoke alarms, forget it". If so, that could lead to improper maintenance of existing alarms, leading to the exact opposite of the intention of the new regulations.
In an ideal world no one would ever die in a house fire, but having four or five inter-linked alarms in every home - even if that happens - cannot prevent all such tragedies. It remains to be seen if these excessive measures will in fact result in more fire deaths by making proper alarm systems prohibitively expensive for some.
Finally, if this policy is to be implemented, someone should tell retailers they could soon be guilty of making fraudulent claims in selling products like Google's Nest alarms, which cannot meet the standard. Even the wired version will not meet the standard because Google doesn't offer a heat-only alarm... even though they are probably the highest-specified, safest domestic alarms on the market.
** There is evidence that common alarms, which use ionising radiation to detect smoke particles, are not as effective at detecting the type of smouldering fire that leads to most deaths. The smart alarms referenced above use self-calibrating photo-electric detectors. They're likely to be more effective at alerting fire before gases render people unconscious. They also don't present a potential recycling nightmare - see blog post below.