you are not going to convince me that this is a normal use for a knife.
Why would I wish to convince you of anything. Since your mind is closed then conversation is pointless. The fact that you aggressively promote the fact that you are unwilling to consider another point of view on a discussion forum is kind of ironic.
If one placed the blade firmly against the wood and struck the spine while applying minimal pressure to the handle, no stress will be placed on the lock at all.
One the blade is in the wood, further force is usually applied by impacting the tip, this will just rotate the blade unless the countertorque is provided by the off hand. This will then produce an internal torque in the knife which will be significant around the lock. However as I noted in the above, you don't need to impact the blade in that manner. you can pick the location so as to produce minimal to no torque on the lock.
From the pics I've seen on a thread devoted to the utility of fixed vs. folding knives, the avergage tree diameter looked to be 6-8".
I'd usually stick to woods which are 2-4". Alders are a local wood which tend to be useful for firestarting as there are usually a lot of dead ones around 1-3" thick and you can just break them off by hand. Gather up an armfull, split a few down the center and make some shavings. Larger trees in the 6-8" range won't actually burn when fresh, local woods anyway. Most fresh woods also have a similar density to water which is 1000 kg/m^3, it doesn't take much size to a tree before it gets difficult to move.
A lot of the time you are seeing people split woods they have cut to burn in a wood stove which is why it is larger, few people cut down 6-8" wood for a camp fire. Beyond just burning, impact splitting is done to make things like spoons and such and you do this with small pieces of wood, again just a couple of inches thick. The same technique is used to make wedges to split larger pieces of wood, split wood to laminate it to give it flexibility, make shingles, etc. . There are many reasons to split, it is much faster than carving away stock, it gives you multiple pieces of wood, etc. .
A general purpose knife is sufficient for this, in extremis.
Generally yes, it isn't that demanding. The common shop/hack knives which are actually made to do it specifically are only 1/8" thick. Ironically, they are actually thinner that most common production folders which are designed "to cut".
-Cliff