@Duke of Marmalade of course the truth of the matter is somewhat more complicated
On the runs
I think this is a reasonable summary of the whole affair.
For the record, the secret nature of this affair was despicable. You will note that, along with SF, the British and Irish governments paw prints are all over this. The legal position was that those convicted pre 1998 were eligible for release under licence the GFA.
The legal position of those not yet convicted was less clear. SF wanted legal assurances that anyone (the otr's) would be eligible for release under GFA terms. This was part of the decommissioning negotiations. As well as that, any prospective prosecution could be a lengthy protracted affair as everyone has an entitled to plead not guilty. Tieing up cases, possibly for years, with net result of automatic prison release seems futile.
So a form of legal assurance was sought.
It became apparent to British government that there was a possibility that its officers could be caught up in prosecution legacy cases facing long-term prison sentences the murky proposal of amnesty was contrived. SF opposed such an amnesty. At least that is what is says here from BBC report
In 2006, an attempt to introduce legislation was shelved in the face of widespread opposition. Sinn Féin's rejection of it, because it would have also covered the Army and police and those guilty of collusion in crimes, made it unworkable.
So amnesty was off the table. SF opposed it. Yes, they would accept it for their own members, which is hypocritical, but not at the cost of letting British agents off the hook.
In the end, SF got the letters for their members while British agents remained on the hook. But not because of any open accountable political process, but because the British government operate a secretive, nefarious political administration in Ireland.
All this huffing and puffing and 'concern' about SF ever getting into power, all the while those in power are at every bit the same game as SF.
"Adulterers in churches and pornography in the schools
You got gangsters in power and lawbreakers making rules
When you gonna wake up! When you gonna wake up!"
- Bob Dylan, 1979.