I've been running YD 25's for 12 years now and changed 300k km of oil and filters and I can categorically state that fitting a genuine filter will result in your oil pressure light going out quicker than ryco or repco. Other brands I have not tried.
The filter on the YD engine is fitted upside down so has an anti drain back valve fitted.
If the valve leaks it takes longer to attain oil pressure on start up after standing for a while.
I contend that the genuine filter has a superior valve.
As for the start up rattle - if its coming from the general direction of the timing chain and quiets down after a few secs , then very good chance its the top timing chain tensioner.
The tensioner is partly spring loaded but also relies on oil pressure pumped through a very narrow galley.
Fact so far but now to speculation -, Either the galley gets partially blocked - or the oil leaks out - dont know how it comes about but you should find that if this is indeed the problem then the rattle should quiet at the same time the oil light goes out, which will be longer than desirable as you are'nt getting full pressure till the tensioner is happy.
So a failing tensioner is not good for your engine on the whole, just as a cheap filter which doesn't hold the oil well isnt good for it.
And if your engine is busy filling the filter its takes longer to bring the tensioner to pressure.
Anyway - I replaced the top tensioner in my D40 and rattle gone.
Chain was fine as per the wear test procedure and the guide showed no noticeable wear.