basically? Obviously this technique can be used on varying levels.
Nihilius restricted her powers to some degree and left her to Sion apparently. But only Visas describes Ni as just a man...Traya says he's no longer human.
She could easily have been prepping it before she even walked in. But once again: That things have changed in the interim. Odan thought his blocking technique was infallible and the greatest power of the lightside.
Yoda does limit himself. However, during the fight with Sidious, apparently either thought using Force powers on one another would be a waste of time...and if it came to it, Yoda'd have his saber through Traya's head before she could blink.Hell, why didn't Malak use the drain on Revan? And offensive attacks are much different than using the force for defense, which is Yoda's preference.
The same Clones they fought with, befriended and trusted for three years and had no malice to be detected whatsoever? The Jedi of the KOTOR ages were getting killed by Atton, too. And Dooku floored Sora Bulq and Anakin...OBi-wan blocked his lightning effectively. And Dooku got that hit on Sora because he knocked his blade aside first....and Jedi don't use offensive force powers? Off the top of my head: Morichro, Malacia, force choke, Electric judgement, force push...
And, ok: One, because the Dark Side is weaker than the light and a true master of the Dark Side will always be weaker than a true master of the light, especially when illusions will mean NOTHING in a real fight. Aleema was a powerful illusionist, so were Luke, the Fallanasi, Volfe Karkko and Palpatine...and Volfe's illusions were tricking trained and true Jedi Masters, Aleema's were tricking Jedi of considerable power.
And Mace was y'know, noticeably unprepared as he just lost his hand to someone he trusted...and only the strongest of Jedi are capable of deflecting force lightning with their bare hands. Only THE strongest. And if the average Jedi will lose to the average Sith Lord, how did a beaten, dominated Order destroy a galaxy full of Sith or how did four knights repulse a battle force of Sith? How did Thon kill the female Sith? How'd revan kill Malak? How'd Hoth send Kaan packing? How'd Murtauugh kill the Dark Underlord, how were Kaox Krul and Rivan killed? Because Jedi master defense and they know how to fight Darksiders. Hell, we saw Yoda send Dooku packing. Yoda might not use the force as an assault besides the general attacks of morichro, malacia, or a force push, but he can sure as hell deflect whatever's thrown at him and outfight his opponents.
He gained a lot of knowledge then, but he already had plenty. Considering he'd been summoning the spirits of the ancients themselves, already had quite a few holocrons and had visited numerous dark side sites, as well as personally having retrieved Kun's personal trove on Yavin 4...and one of the credentials in Sidious's resume was being able to actually fight Yoda, given you have to be Yoda to even compete with Sidious. Hell, by the time Sidious was training Vergere, she knew he'd become the greatest force of destruction the galaxy had ever seen.