As of when, this can be found here: April 1st, 2017 (and it's not been an April's fool!):
The Kodokan has used official technique names consisting of 67 Nage-waza and 29 Katame-waza in the past.
After giving further consideration, two techniques of Nage-waza, Obi-tori-gaeshi (Te-waza) and Kouchi-maki-komi (Yoko-sutemi-waza), and three Osaekomi techniques of Katame-waza, Ushiro-kesa-gatame, Uki-gatame and Ura-gatame were added to the existing official technique names as of April 1, 2017. One technique, Daki-age (Koshi-waza) was deleted from Nage-waza.
Accordingly, 100 technique names consisting of 68 Nage-waza and 32 Katame-waza are recognized as official technique names.
As of why, there is not much more to be found than the opaque "considerations" mentioned in the news itself.
Addendum: This reddit thread discusses (and I think rightfully so) at least regarding Obi-tori-gaeshi and Ko-uchi-maki-komi that it is basically the recognition of distinct techniques successful in sports Judo (Obi-tori-gaeshi is basically a Khabarelli) as such.