Why is tin loaf bread not usually scored like other forms of bread?
If you look at your videos again, you will notice that the loaves did rise a lot during the second rise in the tin. They were fully proofed and therefore the oven spring (the expansion in the oven) is minimal. Plus, they are both baking at relatively low temperatures.

Bread can be baked at different stages of proofing, you may have heard of the poke test - essentially indenting your loaf and see how it springs back - to determine when a loaf is fully proofed. Catching a full proof is a tricky thing because on the other side of “full” lies “over-proved”, which for free-form loaves means essentially a collapsed bread instead of oven spring. So for many free form loaves, bakers will bake at a “well-risen, but not yet fully proofed” stage and slash to allow for the greater expansion of these loaves. Slashing a fully or even slightly overproofed loaf is a bad idea, it will likely collapse the bread. Steaming also helps to keep the crust pliable for a bit longer.

A bread in a tin can also be scored, but you can go for a full proof with less risk: If you overproofed slightly, the tin will still hold the bread together where a free-form loaf flows outward. If you look at your videos, you will notice that the bread rises a lot before going into the oven and only a bit during baking.

The type of bread is also a factor. Your videos show a classic white sandwich loaf. This kind of bread has a rather fine crumb structure with lots of small holes, achieved by kneading after the second rise. This type expands very evenly, which means less uncontrolled bursting. And finally, both bakers use rather low temperatures (180-200 C is low in bread baking terms), which means the top crust won’t set as quickly as at hotter temperatures and the oven spring is also a bit slower and more regular.