Inflation caused by currency debasement is very much not a flat tax - the major effect of it is not on the prices (though some inertia and 'stickiness' of e.g. wages definitely applies as you note) but on all cash-denominated assets and contracts, especially lending.
In particular, it's a tax on all savings in cash and bonds (but not on investments in stocks), and it's a boon to all debt. For example, the total housing mortgage volume is huge - so if currency debasement causes any significant, rapid, unexpected inflation (expected inflation is priced in the interest rates) then it's a significant shift of wealth from the lenders (and, correspondingly, to all people and businesses holding money in banks) to the mortagage borrowers.