Btw, i think there is a third way to create the ISO that could be convenient
First thing you should use is a flag in the PARAM.SFO/ATTRIBUTE that allows to create a "not bootable" bluray structure. In other words, it doesnt contains an EBOOT.BIN because cant be booted
Is the flag named
Install Disc (decimal value 65536)
https://www.psdevwiki.com/ps3/PARAM.SFO#ATTRIBUTE
And additionally to that... there are 3 available ways to include PKG files in a bluray disc, also known as:
-PKGDIR
-PS3_EXTRA
-INSDIR
Probably all you know the first 2 ways, with PKGDIR the install pkg icons appears like an standard ICON0.PNG, with PS3_EXTRA appears like in "what's news" (a floating window)
And... INSDIR installs all the pkg's automatically, the pkgs are not even visibles, and are mandatory to install when you click in the game icon... after all them has been installed the PS3 boots the EBOOT.BIN