Was this posted already? This is the same experience I have, no LFC below 48fps even if the game runs in 120hz mode.
I don't get why people keep saying that LFC is working and have no examples to back it up.
Without appropriate special tools, it is not so easy to tell by pure observation whether LFC is working as it should.
Unfortunately, the YouTuber you linked has already made many mistakes and false statements in the past regarding VRR and LFC, he says it himself that he is not familiar with the technology behind it.
Don't get me wrong, he may indeed be showing a problem with the PS5's LFC implementation, but he can't make the statement that LFC doesn't work at all.
Let's take a look at the frame rates in his video:
50 -> 48 -> 118 -> 47 -> 118 -> 76 -> 50 -> 118 -> 73 -> 118 -> 67 -> 118 -> 72 -> 118 -> 71 -> 47
These values are an
indication that LFC does work to a certain extent. The values in the 70s range are most likely due to render speeds around 35 FPS rather than actually being 70FPS. Jumps from 47 -> 118 -> 76 support this thesis, which actually may correspond to a fluctuating rendering rate like 47 -> ~35 -> 38.
However, every FreeSync implementation from AMD deactivates variable frame times (including LFC) when falling below a certain frequency / exceeding a certain frame time.
And from the looks of it, that lower limit is set relatively high on the PS5, similar to the lower VRR limit.
Looking at the numbers above, it looks like LFC on the PS5 is only active in the range between 35 and 48Hz. Of course, this may lead to judder in games with strongly fluctuating frame times, despite LFC being active.
I must emphasize once again: without special tools or a controlled test environment, however, this cannot be said with conclusive certainty.
We would need something like the Pendulum Demo with which we can determine the parameters of the rendering output ourselves.
As a side note:
LFC is not just a simple multiple output of the same rendered frame. LFC implementations try to make the transitions of the frame times as smooth as possible. I.e. it tries to compensate for sudden jumps in frame times, which lead to clearly visible judder.
As an example, a game outputting with a fluctuating frame rate like 30fps -> 35fps -> 25fps -> 35fps musn't necessarily cause a frame rate of 60 -> 70 -> 50 -> 70 but sth. more smooth. (using frametimes would actually be better to explain this but I want to keep it simple)
The technically savvy can look at
AMD's FreeSync implementation including LFC in the Linux drivers, which are open source.