Osmo Pocket footage bitrate tops at 100 Mbps. On observations I found online, for the footage shot with the same camera, 4K/25 has 80Mbps and 4K/60 has 100Mbps. Does it mean that 4K/25 in this case has better quality or detail for each frame?

If 4K@25 fps have 80 Mbit/s and 4K@60 fps have 100 Mbit/s, then no.
Since a frame is a still image and 80 Mbit/s is 20% less details than 100 Mbit/s.

But I haven't checked if it is only 80 Mbit/s if you shoot @ 25 fps (I have Pocket 2).