Does video play in MediaBrowser force transcoding?

I am trying out Serviio on a QNAP NAS, and it is generally working pretty well, so I've been considering springing for the Pro license. Because the NAS processor is not very powerful, I have transcoding disabled in the Serviio Console. However, I am noticing that when I try to play a Movie video through the MediaBrowser, the video stutters and the ffmpeg process is running (for a very long time), plus I can see that it is creating some kind of very large temporary file in the tmp folder. So apparently it is forcing transcoding, even if transcoding is turned off?

I know that my browser (latest Firefox on Windows 10) is capable of playing the video (MP4 with SD H.264 AVC video and AAC audio) without transcoding, because I had previously been using Plex, and it played quite well in Plex Web without any transcoding. I do realize it might not play in all browsers/OS versions, but if there was a compatibility issue, I would have expected an error indication rather than forced transcoding overriding the setting. Can anyone provide some insight here? Thanks.

Oops, never mind, I think I found the answer here:
viewtopic.php?f=5&t=21774&p=107655&hilit=mediabrowser+transcode#p107655
Which basically says you can't turn off transcoding for MediaBrowser. Unfortunately, that kind of makes MediaBrowser not very useful to me, and thereby makes the Pro license also not very attractive.