The WitchKing and Gothmog

[obloquy]

However, just because he made the statement does not mean he would have changed things he already made. Tolkien was increasingly reluctant to change things in print.

It tells us that he had a new idea for the Balrogs of the earlier stories. He was not in the slightest reluctant to change things "in print". He changed his hand-written and typed stories very much. Don't forget that none of the Silmarillion had been published when this note was written.

In addition his memory was not what it used to be in his old age and the fact that he would consider having only 3 Balrogs shows this.

The suggestion of reducing the Balrogs' total number to three is not evidence of dotage, as I have seen implied many times. What is so outlandish about three Balrogs? Implementing the change of quantities to a maximum of seven would already be modifying the existing stories radically, why is reducing the number to three so impossible? There need only be three Balrogs: Gothmog, Durin's Bane, and Glorfindel's Bane. All of the other thousands could be eliminated with no drastic change. In fact, retaining the thousands of Balrogs, in light of the Balrogs' LotR "power surge", would be ridiculous.

To presume that anyone could know for certain Tolkien's latest intentions is ridiculous.

It's not strictly presumption. The note is the latest idea as to Balrog numbers in writing by Tolkien. It dates after all other materials, and was attached as a tentative change to the Annals of Aman.