We all understand that a word in one language may require multiple words to translate into another language ... and that this is not "added" words as there is no added information. In fact, when I translate ἐστέ as "you are", I may be loosing information if the context does not make it clear that a plural subject you is intended.
However, we are less clear in those cases where the LEB flags a word as "added" what is going on. However, Logos provides the tools for us to track it down.
1. For an example, we will take the final "him" in Matthew 27.31 - shown here in both the ESV and the LEB.

2. Note the LEB has an asterisk noting the added word. Notice popup.

3. So why the added pronoun? The note indicates that it is to supply a direct object. If you read the sentence without a direct object in English, you will feel the language is "stilted". To verify this gut reaction of a native speaker, one can check the Case frames for English verbs from Martha Palmer's site.

As you can see all the frames in English require a patient role (direct object) so that an English sentence without a patient is semantically ill-formed.
4. However, as the BWS Case Frames for the Greek shows, in Greek the verb does not require a patient although it often takes the same forms as the English frame.

So the question is: in translating does moving information from implicit to explicit in order to meet the semantic role requirements of the target language "adding words"? I personally don't think so and prefer the terminology "making the implicit, explicit". I prefer to reserve "added words" to refer to things not required in moving from the source language to the target language. Just like I don't think of "grammatical gender" as something lost in translation when it doesn't exist in the target language (English).