Two things I would like to point out.

these shots successfully suppressed sperm production in nearly 96 percent of men who completed the study.

Those few percent between male and female birth control effectiveness are huge. when used correctly most female BC pills are 99+%. Source hell condoms are 98% (when used correctly)

Also

When the trial concluded, more than 75 percent of the participants said they’d be willing to continue receiving the shots as their main method of contraception.

It's unclear if the 6% or so that got the side effects were the ones that would not want to use it, but it seems clear that there is a large market/desire for this kind of thing even with possible side effects, but I personally would not be willing to trust this soly at 96%

It's great that this study was done, hopefully work like this will continue to be done to give individuals and couples more control over their specific contraceptive needs.