Does gaining an armor proficiency from your class also give you the ability score increase from the corresponding armor proficiency feat?

Question

Old school RPer coming back after long gaming hiatus and new to D&D 5e. Liking what I see, and happy to be rid of THAC0, lol.

As I'm reading, it seems feats are a little different now and fewer and further between when leveling, so I'm guessing they're more valuable than they used to be. Going through the feats list, I noticed that a lot of the feats also give an ability score increase; I have a question about those increases.
(Example: the Moderately Armored feat gives proficiency in medium armor, and also increases Str or Dex score by 1.)

If I recall correctly, in the old system, if you were proficient in an armor type, you effectively had the armor feat for it.

Does a class in D&D 5e that starts with proficiency in medium armor have the Moderately Armored feat and get the corresponding ability score increase (+1 Str or Dex)? Or is the feat totally separate, and they can just wear the armor but don't get the ability score increase unless they take the feat?

Answer 1

No, it doesn't

When you start with an armor proficiency, you do not automatically have the feat that would otherwise grant that proficiency.

In D&D 5e, feats are an optional rule, used if the DM allows them. Variant Humans are the only characters to get a feat at level 1 based on the rules; otherwise, any character can take a feat instead when they gain the Ability Score Improvement class feature (if feats are allowed).

Answer 2

No. Medium armor proficiency is not the same thing as the Moderately Armored feat.

If you take the Moderately Armored feat, you gain medium armor proficiency, shield proficiency, and +1 to Strength or Dexterity.

If you merely happen to have medium armor proficiency from your character class, all that happens is you have medium armor proficiency. That's not a feat, it's a proficiency.

Answer 3

No ability scores are adjusted based on starting proficiency. Feats are an option add on to the rules, unlike some previous editions, and no rule outside of the feats depends on them.

Answer 4

The basic rule for armor states:

Anyone can put on a suit of armor or strap a shield to an arm. Only those proficient in the armor's use know how to wear it effectively, however. [...] If you wear armor that you lack proficiency with, you have disadvantage on any ability check, saving throw, or attack roll that involves Strength or Dexterity, and you can't cast spells.

Armor proficiencies come from either your class feature or a feat and they will be clearly listed for you. Proficiency is a separate can of worms from attribute scores/bonuses. You can gain proficiency or attribute scores/bonus without the other. In fact, the only source that grants both simultaneously is via a feat.

Normally, when you reach certain levels in a class, you get the Ability Score Improvement class feature, which lets you increase your ability score(s) with a pair of +1 increases (or one +2 increase). Feats are an optional alternative to getting those +1 increases.

At the relevant levels, you have to choose between getting the +1s to your attributes or taking a feat (if your DM is allowing feats to be used). You don't get both:

At certain levels, your class gives you the Ability Score Improvement feature. Using the optional feats rule, you can forgo taking that feature to take a feat of your choice instead.

Some feats include a +1 attribute increase in addition to their other benefits. It happens to be that most of the armor feats are like this but you don't get the benefit of the feat as a result of your armor proficiency. Quite the opposite: you get your armor proficiency as a result of the feat (if and when you take it).