"Usage of Online Features is not allowed."

The online features in Let's Go would negatively impact the run. You would not want to slow down time with an online trade or battle. You may be interested in the DLC (but as of 2019-07-17 the only relevant DLC is 100 extra PokeBalls which would help with money planning in the earlier of the run.)

Nonetheless, I feel this rule is extremely vague. The rule is not: No Mystery Gifts or No Trading Pokemon. So, the rule is vaguely restricting use of Online functionality. Without an active Internet Connection and/or the Nintendo Online Services, the Nintendo Switch allows Pokemon Let's Go to perform the following:
• COMMUNICATE: Local Trade
• GO PARK: Bring Pokemon

I would like to confirm if these functions of the game that are NOT online features are considered by the community to be acceptable for the run? (Cause currently the rules for the run do not address this.)

I have no doubt that you are intentionally acting like you are not understanding what that rule is supposed to restrict.

@wartabwartab, I do not appreciate your negative implications directed towards me solely because I bring up a valid point.

Contrary to the cynicism, I legitimately do not appreciate grey areas within any documentation labeled as "rules." While I am newer to the speed run community, I still adamantly feel there should be no grey shades within the rules as this only complicates things unnecessarily for those new to running.

sarcasm must not exist in canada