I would say
because Jesus Christ is the only Mediator between God and men hence according to the will of God. That means the "he" in the KJV is the "he" that searches our hearts and knows the mind of the Spirit and so that he in the conclusion of that verse cannot be "the Spirit".
You had identified Jesus as that "he" that searches our hearts for why it cannot conclude as the Spirit at the end of that verse.
This is why Jesus alone is at that throne of grace to answer prayers for when the father gives permission for the Son to answer that prayer.
Hebrews 4:12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart. 13 Neither is there any creature that is not manifest in his sight: but all things are naked and opened unto the eyes of him with whom we have to do. 14 Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. 15 For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin. 16 Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need.
Doesn't say that. Still goes to that throne of grace of Whom we have to answer to and that is Jesus Christ.
Matthew 18:19 Again I say unto you, That if two of you shall agree on earth as touching any thing that they shall ask, it shall be done for them of my Father which is in heaven.
20 For where two or three are gathered together in my name, there am I in the midst of them.
1 Timothy 2:5 For there is one God, and one mediator between God and men, the man Christ Jesus;
Hebrews 7:25 Wherefore he is able also to save them to the uttermost that come unto God by him,
seeing he ever liveth to make intercession for them.
I do not see that in scripture but I do see that when we do not know what to pray for the Father already knows before we ask because Jesus searches our hearts & knows the mind of the Spirit.
Matthew 6:7 But when ye pray, use not vain repetitions, as the heathen do: for they think that they shall be heard for their much speaking. 8 Be not ye therefore like unto them: for your Father knoweth what things ye have need of, before ye ask him.
The Holy Spirit cannot speak from Himself let alone utter any groanings from Himself.
John 16:13 But when He, (
A)the Spirit of truth, comes, He will (
B)guide you into all the truth;
for He will not speak on His own, but whatever He hears, He will speak; and He will disclose to you what is to come. NASB
John 16:13 But when he, the Spirit of truth,(
A) comes, he will guide you into all the truth.(
B)
He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. NIV
John 16:13 When (
A)the Spirit of truth comes, (
B)he will (
C)guide you into all the truth,
for he will not speak on his own authority, but (D)whatever he hears he will speak, and he will declare to you the things that are to come. ESV
John 16:13 When the Holy Spirit, who is truth, comes, he shall guide you into all truth,
for he will not be presenting his own ideas,
but will be passing on to you what he has heard. He will tell you about the future. TLB
The Holy Spirit is serving as the Spirit of Christ. He cannot use any words on His own for why the Son has to know the mind of the Spirit to make the Spirit's silent intercessions known to the Father.
The NIV does not have Romans 8:26-27 right. John 16:13 below proves it as that is the truth fund in all modern Bibles.
John 16:13 But when he, the Spirit of truth,(
A) comes, he will guide you into all the truth.(
B)
He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come.
NIV
May God help you to see that truth. I know I cannot do it.