There are 3 parts of this that are broken though.
1) A Wizard can only learn spells they can cast as a wizard - so a level 1-2 wizard would be limited to level 1 spells that they can learn.
2) You can't cast a Wizard spell with a Sorcerer spell slot - this is the only part you have contested.
3) You shouldn't be able to apply a metamagic feat to a Wizard spell that you learned.
So assuming you are right about 2, the first condition here should prevent you from learning spells above your wizard level - as it does when you are a pure Wizard. A level 1 Wizard cannot learn Level 2 spells. So we have a bug/exploit.
Oh and there is an additional Exploit that lets you keep Wizard spells you learned by leveling when you respec. Respeccing should wipe those spells as if you had not chosen them. In the case of - "well it's a spellbook" - this would be a prime example of why this is an exploit, because Sorcerers don't cast spells from spellbooks.
I know how it should work according to PhB, what i´m saying that maybe Larian chose this approach instead of 2+ different spellbooks, and spell slots, between different casters, as a way to make it simpler.
I shouldn't have included the PHB stuff - just respond to this, it's what I was pointing out.
1)
A Wizard can only learn spells they can cast as a wizard - so a level 1-2 wizard would be limited to level 1 spells that they can learn.2) You can't cast a Wizard spell with a Sorcerer spell slot -
this is the only part you have contested.3) You shouldn't be able to apply a metamagic feat to a Wizard spell that you learned.
So assuming you are right about 2,
then the first condition here should prevent you from learning spells above your wizard level - as it does when you are a pure Wizard.
A level 1 Wizard cannot learn Level 2 spells. So we have a bug/exploit.