Installing piston assembly- girdles

In the video, it seems to indicate that the girdle if you have one should be installed before the piston and con rods in the block. Is there a reason for that? For example the Jeep 4.0 from 1999 to 2004 has a girdle but I think it adds strength but is not load changing.

It is going to be engine dependent. The girdle adds support to the engine block and can aid bearing life. This is normally installed as part of fitting the crankshaft to the block and there will usually be some facility to allow the installation of the conrods with the girdle installed. If that's not the case and you can't work around the girdle then you may need to install your pistons and conrods first. The factory workshop manual will usually advise on the recommended order fo these tasks for your specific engine.