If your int goes up you get skill points In a way so it is like your int was always high. Just like with con increase. Exept con give HP on a temp increase and int dosent, so not at all the same;)
An int bonus granted by a wish wouldn't really be an int BONUS, it would be a change to your actual INT. In which case, yes, I would have it grant the ranks. The reason the headband doesn't grant free-use ranks, is because there has to be a proper way to track what ranks came from it for when the headband is removed. That is why they simply had a specific skill and add the appropriate ranks of THAT skill with the headband. Then, when removed, it's easy to simply remove those specific ranks.
Compare this wish result to an ability increase every 4th level, instead of to the headband.
Yes. This is covered in the PRD section on permanent ability score bonuses:
Permanent Bonuses: Ability bonuses with a duration greater than 1 day actually increase the relevant ability score after 24 hours. Modify all skills and statistics related to that ability. This might cause you to gain skill points, hit points, and other bonuses. These bonuses should be noted separately in case they are removed.
The FAQ for the headband of vast intelligence is a specific ruling for that item which overrides the general rule given above (it's saying that the headband's special assigned skill ranks take the place of the general skill ranks you would otherwise get with an Intelligence increase).
Fast and simple: If a PC manages a 'permanent' increase to their intelligence score that works when they are naked for more than 24 straight hours, that intelligence score increase gives them retroactive skill points.
Permanent in this case means the Intelligence increase is with you forever and no longer relies on an outside force to supply it. It is part of the character itself.
Things such as wish spells or magic tomes or the points you spend on level up at 4,8,12,16 and 20 are such permanent changes.
Relevant info:
JJ on skillpoints
We wanted it to also grant skill points, since that's what increased intelligence scores do. What we DIDN'T want was a situation where you get an item that grants an INT bonus and put it on your head and get to pick where those extra skill ranks go there and then...
So the solution was to "hard code" the skill ranks into each item.
Intelligence: If my Intelligence modifier increases, can I select another bonus language?
Yes. For example, if your Int is 13 and you reach level 4 and apply your ability score increase to Int, this increases your Int bonus from +1 to +2, which grants you another bonus language.
Technically, Int-enhancing items such as a headband of vast intelligence should grant a specific language (in the same way they do for skill ranks).
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This FAQ implies all Int boosting items behave this way, not just headbands. [I.e. that Crimson Sphere Ioun Stone.]
Basically, all items that grant a boost have hard coded skills, but wish, as a spell granting an inherent bonus, gives retroactive ranks, I think. The spell definitely gives ranks from that point on.
/cevah
The primary goal is to avoid a character having, say, 6 skill points in Perception and 6 in Knowledge(Arcana) to gain a permanent Int bonus, put 4 skill ranks into, say, Use Magic Device, then lose that bonus and take 4 skill ranks out of Knowledge(Arcana). The secondary goal is go avoid a character taking an Int item and saying, "I feel like brushing up on Stealth today, but I think I'll need UMD in about a week or so." It's the "togglable" nature of item-based bonuses that prompted the ruling on keying skills on item creation. But for non-togglable permanent skill bonuses, it's a non-issue. Fundamentally, this will only be an issue if you have a permanent Int bonus coming from a Supernatural ability in constant effect; the bonus would only go away if you are subject to anti-magic.
The rules for int boosting effects do say that the ranks need to be tracked separately - so that the proper ranks can be removed later on. The headband just makes that even simpler by segregating it specifically.