Sperm doesn’t contain HIV. HIV can only infect very specialized human white blood cells called CD4 cells.
(Caveat: HIV can hide out, inactive, in certain parts of the body, which is why treatment to viral erradication is not yet medically possible.)
The seminal fluid produced in the prostate gland is full of CD4 cells, which is why male ejaculate can have a very high HIV load.
Sperm cells by themselves don’t bear HIV and cannot infect anyone with HIV.
The CDC is sure that durably undetectable people cannot transmit HIV due to compelling, empirical evidence.
A recent meta-analysis of three years-long studies of thousands of sero-discordant couples showed no HIV transmission from the positive to the negative partner, even in the absence of condoms or PrEP.
The long and short of it is, if you take your ARVs every day like you should, and if you see your doctor on schedule for blood work, you are statistically less likely to be able to infect somebody with HIV via sex without condoms than a random gay man would be with condoms.
The CDC is usually very careful with the wording of its announcements. They were very clear last September when they released the results of the partners studies.
Gay men in compliant treatment for HIV who are durably undetectable do not represent a risk for the sexual transmission of HIV.