Is a Pact of the Blade Warlock proficient with all weapons of the same kind as their wielded pact weapon?

Question

According to the Warlock class, the Pact of the Blade Pact Boon feature allows a Warlock to

use your action to create a pact weapon in your empty hand. You can choose the form that this melee weapon takes each time you create it. You are proficient with it while you wield it.

Ordinarily, this would be very simple and straightforward. However, two-weapon fighting makes thing interesting. The Two-Weapon Fighting rule says:

When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand.

With the goal of using the two-weapon fighting rule above, let's use a shortsword as an example. Shortswords are martial melee weapons with the light and finesse properties. As such, they can be used for two-weapon fighting, and Warlocks are not proficient with them.

Now, perhaps I'm over-complicating things a bit... but it seems to me that there are two ways of reading that last sentence in the Pact of the Blade quote from above:

1. It could mean that because the Warlock has created a shortsword as their Pact weapon, that they are proficient with all shortswords while they have their pact weapon in hand. This would, in effect, temporarily add shortswords to their weapon proficiency list, and allow the Warlock to make a proficient shortsword bonus-action attack from two-weapon fighting.

   OR

2. It could mean that the warlock only has proficiency with their pact weapon; if they wanted to make a proficient bonus-action attack, they'd have to use a simple weapon in their off-hand.

Thus, my question is:

Does a Pact of the Blade Warlock have their weapon proficiency list increased while their pact weapon is active? In other words, is a Pact of the Blade Warlock proficient with all weapons of the same kind as their wielded pact weapon?

Answer 1

You are only proficient in the specific weapon you summon

The feature in question states:

[...] use your action to create a pact weapon in your empty hand. You can choose the form that this melee weapon takes each time you create it. You are proficient with it while you wield it.

The word "it" in the final sentence refers to "a pact weapon" and "this melee weapon", not to "all weapons that are the same type of weapon as your pact weapon". You are specifically proficient in the pact weapon itself.

"It" must refer to something used in the previous sentences and we only have a few nouns to choose from: "the pact weapon", "the form", "this melee weapon", and "the form that this melee weapon takes". Trying to substitute those in for "it" only works using "the pact weapon" and "this melee weapon". "It" cannot be referring, in any sort of way, to the entire class of weapons that your pact weapon happens to be a part of.