No one is assuming. He had unprotected penetrative anal sex and he needs to test to know his status.
Everyone obviously knows there is a risk with unprotected sex. But, some forms are more riskier than others. I do not like to assume.
Go test an obtain your results and start useing condoms.
Doesn't matter he was at risk and the only way to know his status is by testing.
Were you the giver or the receiver?
You had unprotected anal sex of course you should be concern. You can test now and your test will be conclusive.