>>535523541
I feel like mortal just dislikes tsumogiri riichi, so I wouldn't take the fact that it didn't riichi the kanchan on the following turns as (very strong) evidence that it would prefer shanpon riichi to kanchan riichi

anyway if mortal says riichi is good here then it's probably good
8s or 19s bakyou looks a little good, hatsu has already been discarded and nobody ponned it, so it's not that likely people will chase you with a big dick hand, there's pretty much no improvements if you dama, plus there's 1 honba and 1 stick on the table so winning any hand is more valuable than usual.

so I can think of lots of reasons to riichi, and not too many to dama. the reason you'd want to dama is pretty much to avoid getting chased, but:
with a hand like this and a score situation like this, it would actually be good for you to chase shimocha if he riichied first
kamicha probably doesn't have anything good, seeing the two guest wind tedashi as his last two discards (imagine if you had a big dick hand in deep 4th - would you ever keep any safe tiles? my read off of him keeping the guest winds over 12p penchan is that he's coping for distant souzu honitsu)
dealer chasing would actually be pretty bad. but it's not like he's guaranteed to chase you

I definitely don't think that this is some obvious by-default riichi. For a borderline hand like riichi nomi terminal shanpon wait, the riichi decision should be based mainly on the bakyou, but with this bakyou riichi should be heavily favored.