The GH5, like most other "DSLR" type cameras and most drones, uses long-GOP codecs. Long group-of-picture codecs use one complete stored frame, called an I frame, typically every 9-15 frames. In between they store only a matrix or data-set of the ​pixels​ that have changed since the previous complete I frame, or before the next one ... those are called p and b frames, though there isn't actually a frame for them ... just a few numbers. So the on-camera chips can be designed to write this format to media quickly, and it takes very little space comparatively.
An ideal solution for the camera makers and camera operators.
NOT an ideal solution for post-processing, however.
​Especially​ as the camera makers and drone makers are now really stretching the number of frames between I frames, while recording in 4k frame sizes. One camera file uploaded in another thread, and examined for the nature of the compression, had 120 frames (!!!!!!) between complete I-frames. Yowza!
To de-encode/de-compress, the CPU takes the first I frame ... decompresses, passes it along and stores it to RAM. Calls up the next frame's data-set ... recalls the previous decompressed frame from RAM, computes the differences, creates that frame as "real" video numbers, stores that to RAM & passes along. Calls up the next data, recalls previous frame from RAM, computes, creates the frame, stores to RAM & passes on ... rinse & repeat.
It is ​incredibly​ intensive work for the CPU/RAM and threads/cores of the computer. Bad enough when it's 1080 media. Horrid when the number of pixels goes up by four times ... from a bit above 2 million pixels to well above 8 million, in "standard" 4k 3840x2160.
All this to say ... you can keep the incredibly small file size ... OR ... you can use a transcode and/or proxy process that edits much more smoothly ... but you can't both keep a single very small file on disc AND edit smoothly. And it isn't just PrPro for that part of the issue. I'm a member of a subscription website for colorist training. One of the ongoing programs there is on building computers for high-end post production work, primarily using Resolve, but also referencing PrPro at times. The expert there points out that if one is insisting on grading original long-GOP material, the build design of the machine best suited to that gets very specific ... and includes other limitations the colorist probably doesn't want.
One regular here who works with such media routinely creates transcoded files on uploading to the computer using Cineform, named exactly as the original media. The original media is put in the Archive files setup he's got, he uses the Cineform (with often Cineform smaller-frame-size proxies) for his editing process. On completion of the process, he puts the entire project into the Archive folder structure with the original media ... but dumps the transcodes/proxies, as he can re-create those at need.
This gets an excellent editing process, and keeps the file size for permanently stored media down.
As to when the GH5 media will be properly seen by PrPro & AME ... hoping they'll have the fix for that & a number of the major bugs out soon. No date is announced, other than they're working on it.
Neil
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