6 chars, Int ranges from 3 to 1
All lvl 6.
3 chars (fighters) lvl6 can dual to sorcerer and see the spells and cast.
3 priests one battleguard and two morning lords can load and see sorcerer spells, but immediately gets the "beyond sirceror casting ability"
All the fighters can see and use the sirceror spells.
If I reload, level the clerics to Wizard, they can learn then cast perfectly off any scrolls.

Sorry split post..
3 clerics can learn wiz/sor spells at int 3 and int 1, but get the "beyond wizard capabilities." Message.
One is wild elf with favoured class sorcerer.
The 3 fighters who are ALSO int 3, can become sorcs, BUT they can cast.

So this means that cleric/ sorc dualling isn't allowed and not that int/wis is requiref

You know that sorcerer spells are based on charisma, not int?

If this is IWD then it's working as intended as Sorcs aren't allowed to multi class under 2nd Edition rules.

If this is IWDII then you should be able to multi class into Sorc because 3rd edition rules allow it.