“But thanks be to G-d who puts the same earnest care for you into the heart of Titus.”
II Corinthians 8:16 NKJV
Titus doesn’t get the credit G-d does.
“And whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks to G-d the Father through Him.”
Colossians 3:17 NKJV
It appears evident to me that G-d gets all the credit, all the time. For whom seems to fit best because the churches are also showing gratitude. If it were to whom, I would have found it reasonable to see Paul follow up and express the thankfulness the churches want to communicate to the couples because they don’t have contact with the couple. Yet in the case that the churches are being thankful to G-d the churches can do the thanking directly to G-d not needing an intermediary like Paul to communicate their message to G-d of thanksgiving.
It isn’t obvious enough to me that this could be an exception, even though multiple translations including non English translations say to whom.
““Or who has first given to Him And it shall be repaid to him?” For of Him and through Him and to Him are all things, to whom be glory forever. Amen.”
Romans 11:35-36 NKJV
It is only fitting that if the Spirit is given dominion over our bodies, that the Spirit receive the gratitude for the deeds He executes through our complete surrender, unless we believe there is something we can do outside or apart from the vine.
““I am the vine, you are the branches. He who abides in Me, and I in him, bears much fruit; for without Me you can do nothing.”
John 15:5 NKJV
If we can do nothing, then it’s clear it’s He who deserves the gratitude.
Also it’s not both the couple and G-d being thanked it’s either one or the other in this passage. So it would stand to reason that the causing agent should receive the gratitude not the instrument He is using, which in this case He also happened to have being the Creator of and has imputed His Spirit to transform them, guide and direct.
Furthermore so far I’ve not found one instance in the OT or the NT where a human gives thanks to another human. All the thanking is directed to G-d.
I’ll use an illustration to make a point from logic to hopefully bring all this home. Obviously illustrations are limited so please take it for what it’s worth.
If I’m trapped in a car that just plunged into a lake taking in water and a farmer with a stock horse is close by with a rope, in the event that the farmer ties the rope to the car hitch and pulls the car out of the water before I drown trapped inside: if I am going to thank one and only one, would it be the horse who did the work or the farmer who saw the need, created a solution, utilized his resources and directed the horse?
It’s for this reason I cannot see this text being interpreted both ways, you cannot equally interpret it either way, thanking both the couple or G-d. And since it is a little ambiguous, and only one party is receiving gratitude from two sources (Paul and the churches), and G-d is much more Other than the couple, and He gave the couple the resources and changed life, I reason that it was directed toward G-d and not the couple which if it were the couple would be to my knowledge the first instance and the exception where a human received thanks from another human in the Bible.
Also to reemphasize,
“for it is G-d who is at work in you, both to will and to work for His good pleasure.”
Philippians 2:13 NASB
Why would the couple be thanked for that which G-d was at work for in their lives?
“A text without a context is a pretext for whatever you want it to mean”. That’s why to me I place a lot of value of contextual analysis both narrow and wide scope context. Individual word analysis especially ambiguous ones are open to personal interpretation/opinions/preferences without a broader context
(I am open to being corrected and have no issue being critiqued in fact I find it helpful and loving of someone to point out my blind spots.)