"So I am going with the fact that this person is NOT a dependent from above explanation. Correct me if I am off base on this. Thanks"
The eligibility for #3 are different than the others. The letter would be triggered as a "might be able to" condition, based on whatever tax filing(s) existed for that name at the time the RRC was projected and sent.
Don't go from the above explanation. Work through the IRS wizards and eligibility.
The third Stimulus payout which started in Jan 2021, has different eligibility rules as to dependents and this payout is a projection, using 2019 or 2020 tax returns, then reconciled against Actuals on the 2021 tax return.
You might want to bookmark these links and read the IRS guidance.
Interactive wizards portal includes one for determining dependency:
"Level Up" is a gaming function, not a real life function.