RTP Payloaders and slice mode for video encoders

I am using the omxh264enc and omxh265enc encoder elements and I am streaming the encoded video with the corresponding RTP payloaders. I just started playing around with encoding slices (using slice-size and num-slices properties. This seems to work, as I see the multiple slices when I look at the RTP packets in Wireshark. However, I noticed that all the slices that make up a frame of video are all sent at the same time according to the arrival timestamps in Wireshark. Isn’t the point of encoding in slices to reduce latency by sending a slice as soon as it has been encoded? Is there some setting I am missing to get the RTP payloader to send each slice when it is ready?