To say Inumaki wasn't curious about why Sherlock kept sighing would have been pure bullshit.
It was just that Inumaki's curiosity was being firmly suppressed by his two classmates and two upperclassmen, especially Kinji Hakari and Kirara Hoshi. Ever since those two learned of Inumaki's curiosity and Sherlock's sighing,
they looked as though they had remembered something unpleasant. With the world-weary faces of people who had been through it themselves, they patted Inumaki on the shoulder and told him,
"No matter what our senior is researching, or why he can't tell you about it, don't get curious. Don't dig into it. Trust us, or you'll never be able to come back."
And Inumaki's answer?
A "salmon roe" full of question marks. The meaning was fairly understandable, probably much the same as Toji's "Seriously?"
Of course, although they wouldn't let Inumaki investigate, the lot of them were naturally still curious about why Sherlock was sighing, so they privately went to Satoru Gojo to find out.
How should one put it? Your dear Teacher Gojo really did have a double standard when it came to Sherlock and his other students. Not only did he make no attempt to conceal Sherlock's terrifying idea for "No-Limits Germ-Type Cursed Speech," but he also told them to keep a close eye on Sherlock and Inumaki. Under no circumstances could they let Sherlock reveal any information about "No-Limits Germ-Type Cursed Speech" to Inumaki by any means.
What? You wanted to know what everyone else thought?
After hearing your dear Teacher Gojo's explanation, they more or less understood why Sherlock had said there was "a broad road straight to heaven." At one point, they even wanted to collectively cling to your dear Teacher Gojo's legs and sing "Father."
Not only did they agree with your dear Teacher Gojo's