How exactly does Might of the Master apply your proficiency bonus to your Homunculus Servant?

Question

Artificers have access to the Homunculus Servant infusion. The Homunculus Servant's Might of the Master trait says this:

The following numbers increase by 1 when your proficiency bonus increases by 1: the homunculus's skill and saving throw bonuses (above) and the bonuses to hit and damage of its attack (below).

However, this phrasing is pretty vague now that it isn't a core class trait. When it was a class feature of the UA artificer's Alchemist subclass, it was given to you as an Alchemist at level 3. So I had assumed that meant that it would get +1 to all the traits from that point on whenever you increased your proficiency modifier.

However, it isn't simply given to every artificer with access to it anymore. It's an infusion you can choose any time you choose an infusion starting at level 6. So... does your homunculus:

1. get your proficiency bonus as a whole added to its stats (so +3 to everything at level 6, increased to +4 at 9, +5 at 13 and +6 at 17)?

2. get +1 to its stats every time your proficiency bonus increases from the point when you do make it? (so if you made it at level 17, it never gets any better than its base stats because your proficiency bonus never increases from then on)?

   or

3. get +1 to its stats every time your proficiency bonus increases starting from the first time you could make it (level 6 on)?

4. get +1 to its stats every time your proficiency bonus increases from the starting bonus of +2, like I had assumed when it was still an automatic feature of the subclass (so it would get +1 at level 5, +2 at 9 etc)?

Answer 1

Option 1, increase the bonus anytime you increase your proficiency, even if you do not have access to the infusion (so +1 at level 5, +2 at 9, etc)

The Battle Smith's Steel Defender also has the Might of the Master feature, is obtained at level 3, and is fairly similar to the Homunculus Servant. This answer is mostly based on logic, as the wording is ambiguous (as you have noticed).

First of all, consider that the text below makes no mention of you having to have learned the Infusion previously. At level 3, even if you haven't learned the Infusion, the Servant's stats increase. They also increase even if you do not have it summoned when you level up.

The following numbers increase by 1 when your proficiency bonus increases by 1: the homunculus's skill and saving throw bonuses (above) and the bonuses to hit and damage of its attack (below).

Secondly, consider that, if stats only increased after you learned the infusion, it would cause two seemingly bad effects: a PC would be forced to take this infusion at level 6 if the PC indeed wanted it; and a multi-classed PC would also be forced to take 6 levels of Artificer to learn this before accumulating other levels.

Thirdly, DnD 5e focuses a lot on simplicity. Option 2 would make you have to register when you had learned the infusion, to count proficiency bonuses from there. It's much simpler to just assume the proficiency of the Servant is the same as yours, period.

That being said, many features in the class are poorly worded. I expect Sage Advice to make an Artificer specific compendium soon.