Definitely C. frutescens you are correct about C. frutescens not having the round shape but there are few that are round CAP 6691 / CGN22080 from Costa Rica is round too I have some seeds I planted some few years back and it was huge bush.
Also, ( Ekirike) is another round C. frutescens from northern parts of South America
i knew that wild annums and chin, tepins, cumari, and other wild ones,all have small round pods full of seeds, funny how all diffrent pepper species all look similar in wild form.