I tried same rgb-scart with same game both in ps2 and psx (soukyu gurentai).
With psx, before actual game started, ossc switched to 263p.
With ps2, ossc showed 525i all the time in menus and in actual game.
Same rgb-cable, same game. Both psx and ps2 are modded PAL machines.
SOLVED! It seems Alundra original runs fine in 314p through rgb-scart when I disabled the modchip. It runs 625i when modchip is on. So it is my modchip that causes the problem not putting ps2 to psx progressive mode.
With component cable, OSSC says no sync, and so does my TV. Since wii component cable works fine with both I suspect the cable even though it feels strange that good cable does not work. It has silver cylinders so it is ps3 era as I remembered.
I found following from the internet: “Some of the modchip installations fixed the so called “Greenscreen” problem. This is done to avoid the green tint during DVD playback (when connected via RGB). What the “fix” actually does is to disable component signal completely!”
So it is highly likely that this the main reason why component does not work. I can further test this with other PS2/PS3 console.