I wouldn't classify brother Day as following Joseph Rutherford's lead.
Brother Day is a fine independent researcher and draws his conclusions carefully after much research and prayer.
It should be noted that most Protestant Denominations and the Catholic Church all officially believe that the members of the Body of Christ or the 'Church' will enjoy eternity here on earth along with repentant humankind. They all believe that the members of the Bride will return to this earth and work with Jesus in the great 'restoration'.
So brother Day's view on the Great Crowd of Christians living on earth fits in with some wide spread held beliefs on the future.
We differ with Brother Russell concerning who make up the great multitude of Revelation 7, nor do we agree that the 144,000 are the 12 tribes of Israel spoken of there. (The 144,000 are sealed out of [Greek, ek] the 12 tribes, they are not the total sum of the 12 tribes.) This makes three saved classes referred to in Revelation 7, not two: (1) the twelve tribes of Israel: justified spiritual Israelites, sons and heirs of God who have not necessarily been sealed as one of the 144,000 joint-heirs. (2) the 144,000: joint-heirs with Christ who have been sealed out of the heirs so that they become more than heirs: joint-heirs with Christ. (3) The great multitude, late consecrators here in the end of the age, babes in Christ, who come out of the great tribulaton as an earthly class.
I'm not so sure that Bro Russell is being properly represented in regard to his teachings on the 12 tribes... he stated that the entire 144,000 were intended to be taken out of the 12 tribes of Israel... but it is apparant from NT studies that Israel at large rejected their savior and thus were cast off and the call was turned to the Gentiles... Watch Tower Reprints page 5231; 5532; 4732; 3528; 3026 He taught not that they were the 12 tribes, but that they were of the 12 antitypical tribes...
Had there been tens of thousands of faithful ones in Israel at the time of the first advent things would have gone much differently. He taught that the gentiles for for the most part filled up these places, however the call was never closed to Jews as individuals. R3586 as well as the pages cited above show this.
He also stated or showed that in another vein of thought that the 12 tribes of Israel type the 12 tribes of Spiritual Israel... so that symbolically speaking the little flock class would be (in a figurative picture) of these 12 antitypical tribes... but not all of the tribes... in actuality, the priests of Israel all came from the tribe of Levi...
Additionally, in some places the 12 tribes of the old testament type the 12 main denominations of Christendom...(as well as do the 12 sons of Ishmael)... you will note that in the Tabernacle picture the LF is shown as the priesthood in the court and in the tent... Aaron and his 4 sons (2 of which were unfaithful and were destroyed). The other levites in the court were servants to the priests and assisted them in their work... outside the "fence" or curtains around the court was the nation of Israel camped in their 12 tribes... 3 tribes on each side... while the priests of Israel were all taken from the tribe of Levi... as to the Little Flock, they were taken from the 12 denominations during the Gospel Age... for there was a time in each one of them when they had the truth that was due at the time...
As Rev 7 shows the 144,000 are taken from the tribes (antitypcal tribes) of Israel... it is clear in the Scripture that the 12 groups of 12000 are ALL the 144,000... but that they were taken out of all of the tribes (all denominations as to gentiles and all tribes as to Jews)... but they were not all there was as to the tribes... not all were chosen... in fact "many are called , but few are chosen"... The next class discussed (the great multitude) were those called but NOT chosen... Rutherford created them as an "earthly class"... Ron Day is following his lead.