Missing "time_off_type" in /company/absence-periods response

Hello,

there is no possibility to find out what kind of TimeOffType has an absence period.
In /company/time-offs response there is an object:
"time_off_type": {
"type": "TimeOffType",
"attributes": {
"id": 54321,
"name": "Vacation",
"category": "offsite_work"
}
with the "category"-attribute, which can be found in the /company/time-off-types response.
But /company/absence-periods has no such data. Why?