Proposal Ask FullFact is for "anyone who wants a statistical claim made by UK politicians, or the media, to be factchecked"
But any statistical claim made by a UK politician would count as a notable claim and be within the remit of skeptics.SE. So the proposal is just a subset of an existing site, and would take traffic away from that site.
That's not in any way to denigrate the marvellous work that the FullFact team do. I'm really glad they exist, and do such a good job. It's just that skeptics.se already has this angle covered within the Stack Exchange Q&A format.