Signature Spells are costing prepared spell slots

I searched for this and couldn't find it. Apologies if I missed it somewhere else. 

The level 20 feature for Wizards, Signature Spells, gives two level 3 spells that are always prepared. Your level 1 spellcasting feature says "If another Wizard feature gives you spells that you always have prepared, those spells don’t count against the number of spells you can prepare with this feature, but those spells otherwise count as Wizard spells for you." That means, at level 20, I should have 25 spells prepared IN ADDITION TO, all the spells that are always prepared. However, if the two spells selected for Signature Spells were already prepared (as they most certainly would be), they DO currently count against your 25. To fix this, I had to remove them from my signature spells, then go remove them from my prepared list, then go re-add them as signature spells. That left me at 23/25 with them marked as always prepared.

How it SHOULD work: selecting them as signature spells SHOULD remove them from your list of spells that count toward your 25 and mark them as always prepared.