In old version the border style was correct dashed in following sample:
@startuml
/'
skinparam package<<boundary>> {
StereotypeFontColor red
FontColor red
BorderColor red
BorderStyle dashed
}
'/
skinparam rectangle<<boundary>> {
StereotypeFontColor blue
FontColor blue
BorderColor blue
BorderStyle dashed
}
rectangle "R1" as r1 <<boundary>> {
rectangle "R2" as r2 <<boundary>> {
}
}
@enduml

(the (package) font color handling was "special" in the older version too, and is not important in this issue. I used it only as marker that the styles are assigned)
BR Helmut