That sounds about right. It is hard to make all information public asap (with all the regulation), so I would assume it would be hard to get rid of the wiggle room between when an insider can place a bet and the information actually becomes public
Matt Levine's most recent article touches on insider trading pros and cons (in relation to sports betting) and is, as usual, a great read - https://archive.is/jJ25g
If that is true, then markets would be even more efficient is such information was made public immediately.