Quarantine Report - no action available for some spam

[ToffenDask]

I've struggled to get an explanation from support about a behavior we are frequently seeing in our environment. In the below quarantine email digest, why is there no "Trust sender" action available next to the last email item in the list? Interestingly, the old (?) documentation at https://www.avanan.com/docs/spam-protection includes a screen shot of a sample report, also missing the Trust sender action for a few items. No explanation as to why, though.