Roman Empire Exclusive Technologies Bug?

Men-at-arms are one of the focuses of this civilization.
For this reason it is possible to add some technologies to improve them, to “heavy maces” and “two-handed weapons”, the first one gives you +6 against heavy units and the second +2 damage to the unit.
Together it should be +8 damage against heavy units, however the “heavy maces” tech now gives you +3 after you take the “two-handed weapons” totaling +5.
Is this on purpose?
Ps. Language of images in portuguese

I felt that it was explained as its a “one or the other” kinda of upgrade… but maybe i was wrong or thinking of something else