So, the Magus has this special diminished spellcasting which it loses the lower level spell slots whenever it gets a new spell level from Level 5 onwards.
Martial Caster feat aside, does the Magus lose the ability to cast lowered level spells from a Staff? It seems counter intuitive but that's what the Staff rules state.
You can Cast a Spell from a staff only if you have that spell on your spell list, are able to cast spells of the appropriate level, and expend a number of charges from the staff equal to the spell’s level.
The Magus can cast a heightened version of a level 1 spell, which counts as a higher level spell from what I understand, but, if he is level 5 or higher, he cannot cast a level 1 spell.
Is this an oversight or am I reading too much into things?
RAW it would look like it.
But on the other hand, the spell in your spellbook is not the heightened version, different from the learned heightened versions spontaneous casters learn. True Strike is still a 1st level spell there. Only once you prepare it, it's a higher level one. So technically you still can cast lower level spells, but you heighten them in your spell slots. The opposite is not true. you can never cast a 8th level spell with a 3rd level spellslot.