"It "feels" like the flaw in the thinking was that it was just an HR matter."
I agree with this. The IO was a very senior HR civil servant & would have been expected to have the professional knowledge & experience to know what 'no prior contact' meant both in theory & practice. And there was clearly inadequate oversight at a minimum.
But it's the decisions made once that was known to be a major issue that are the significant concern over Sturgeon, Evans, Murrell etc.
Nothing said today explains things to the satisfaction of many, but I fully expect sturgeon to think she can brazen her way through the furore.
The ministerial code investigation is probably where she's most weak & then there's the VONC to threat too. I've no idea what the final outcome will be, but I don't think she's fit to continue as FM based on both her evasive & unconvincing answers, her own decisions/actions throughout & her blind faith in the civil service in particular. Evans should have been sacked. No question in my mind that she shouldn't be employed - instead, she got a pay rise & extended contract.