I can’t read the article, because I’m not a subscriber but, although the BBC headline says he thinks they should be compulsory, the nearest they get to quoting him saying that is that he thinks “there’s no reason not to”, which isn’t the same thing at all.
That’s like me saying there’s no reason not to pack some snacks before a long drive – no suggestion it should be compulsory, just advice. And coming from his background of competition, where they are compulsory, he may not have thought through the “reasons not to”. I wonder how many times Boardman came out as a helmet-sceptic while he was still competing (I don’t know and I support and admire him and his stance as an advocate for cyclists’ safety, now, so this isn’t a criticism).
The BBC has policies on helmets – presenters, I believe, are not allowed to appear on a bike without a helmet (although, presumably, they can’t compel guests), which is part of normalising helmets despite the issues/doubts which are well documented. Headlines like this back their pernicious campaign for cumpulsion.