Nathan,
I'm guessing you haven't read the sticky at the top of the forum on hot load posting. It's one of the items all posting members should read.
It is here. While the title refers to hot loads, about two lines down is the "However", which says to use the warning for anything outside published load recommendations, meaning, regardless of your own experience to the contrary.
For the board, it is absolutely about law suit defense cost avoidance. For yourself or others reading about the load, I'll throw in a caution: Elmer Keith developed the .44 Magnum just using 16:1 lead:tin, which is softer than the Berry's you are shooting, so the expectation is that you should have no issues. However, a manufacturer receives feedback from many customers, and it sometimes happens that they learn of unexpected and unexplained anomalous behaviors and adjust their load recommendations to avoid the conditions that produced them. Without Berry's data, you won't know whether that's the reason for their recommendation or not. If there's been a dangerous event, for liability reasons their attorneys will not want them to speak of it.
The example that springs to mind is Alliant's warning not to use Blue Dot with 125 grain bullets in .357 Magnum, but all other bullet weights are OK in that cartridge. They also don't want Blue Dot used in any .41 Magnum loads at all, but all the other chamberings are OK. It's a very peculiar warning. Rocky Raab said he had a nice conversation with Alliant at the SHOT show right up until he asked about this warning. At that point the friendliness turned off and faces went dark and he got nothing more out of them. They clearly just weren't allowed to talk about it, implying something bad happened to some persons. So they had adjusted their load recommendations to avoid recurrences. If you ignore their advice, is there a high probability the bad thing is going to happen to you, in particular? No. Lots of people have shot Blue Dot in the proscribed manner. Is it likely to happen to someone? Yes, since it's obviously happened before. Is there zero chance you will be that someone if you ignore their recommendation? No. That's just how the dice roll.
So, for the individual loader, the caution is simply to alert them that by ignoring the manufacturer's published limits they may be rolling dice even if they follow proper load workup practice. We can't really know without the manufacturer being able to speak candidly.