For possible talks about the forming of a coalition with the SPD or the Green there can only be one basis: the party program of CDU and CSU. In there you will find nothing about either tax increases or higher debt - quite the opposite! The foregoing of higher taxes and higher debt is a brand essence of the Union.
I think that for him higher taxes and higher debt are more than random phrases he knows little about, other than that both are bad. So, for him it makes sense to put them into a sentence. Of course, higher taxes would mean higher revenue and therefore lower debt, but Seehofer doesn't care.
Fun fact: he also ruled out a coalition with the Greens just a few days ago. He doesn't seem to do that anymore.