Like most fabrications with tools and materials, there are many methods or ways to complete an operation. Any and all power tools can be and are dangerous if not used poperly.
The operation you are talking about is done this way for a specific reason!
By using this method to SIZE the sheets. you end up with in this case 4 sheets that are all EXACTLY the same size in height.
No other way to do this.
The real fun is when you do this with 1" thick sheet material that weighs 200 lbs and cost big $$$$ . The HOBBY table saw / router table you see in pictures can not complete that work with the precision required.
A 4'x8'x2" thick router table with 4ft and 8ft fences is used, and yes you have to trap the material in order to mill it to exact size. Takes time and care but imho its easy and safe as any other shop operation.
You want to see some unsafe shop work stay tuned. Making small parts with big power tools is imho the dangerous work. Milling big sheets of plastic is easy and safe compaired
And this is not safe and not being used properly.
Yes, you can get parts exactly the same size using traditional methods. It's done all the time in woodworking.
I've got 4, maybe 5 routers. My largest is PC's largest (and most expensive) and is a beast.
A friend of mine was an acrylic guru. Use to build windshields for boats. Large boats. (plus cabinets out of acrylic. This guy was good) Taught me the little I know about working with it. I've consistently gotten parts exactly the same size using normal wood working techniques. I've also done it the same way you have shown.
The way you are showing is NOT for a newbie who isn't 100% familiar with a router and how it can hurt the acrylic. Not to mention lost digits.
As for all the sheets being the same size. While true, all you have to do is lose concentration for a nano second and you'll have a divot. All the panels will be the same size though. And all the sides may be the right size. Without following proper technique at the saw you may find you have a parallelogram instead of a square/rectangle.