I see your point of view.
There are marked differences, the spotless thorax (although it is bald), the FW basal black streaks instead of spots, and the non-extension of the zigzag line to the FW dorsum.
However, the general pattern is so strongly similar it can only be in the same or closely allied genus.
A check of the tribe Lymantrini shows no other genus other than that stated in Moths of Borneo. (Checked funet )
None have a match not even the closest Psilochira.
I think all the images of I. munda on the web are males, so there is a possibility it is only a female I. munda.
However, if the female is so different then Moths of Borneo would shown one since they have a specimen.
Could it be a mimetic species from another family ? I think this is rather remote.
TL Seow