I see no reason why they would want to conceal the bloodstain. However, if the blood stain on the Bible came from that stain, that's not coincidence. That's why it's important to know where the blood stain came from in the first place.
Caroline has proven that the stain on the bible did not come from the carpet. The stain is on the wrong side for that.
http://jeremybamberforum.co.uk/index.php/topic,4616.msg191520.html#msg191520"So, IF it was placed there by Jeremy just after shooting Sheila the pool of blood would have to be wet at the time it was placed there - so why is there no stain on the page that would have been face down on top of the blood? The stain MUST have been dry when the bible was placed there and as such could not have been placed there by Jeremy Bamber."
At the red forum Myster showed that the bible is open at a different page on the floor to the one which shows the stains.
http://miscarriageofjustice.co/index.php?PHPSESSID=rt32johmi44hdos93lvd0a3171&topic=7970.msg386328#msg386328"The bible in the crime scene photo is not open at the pages which are bloodstained (656-657). Look at the difference between that photo and the recent one using a new identical copy of the bible. The original bible is opened towards the end of the book, whereas (stained) pages 656-657 of the copy are in the middle of the book. Easily recognised by looking at the spine in both photos."
An interesting question is how do these two points relate to each other. Caroline made the point that the bible must have been put over the stain when it was dry, otherwise there would be a stain on the left hand page. But at that stage she appears not to have have been aware of Myster's point, that it is not only true that the stain is on the wrong side, but also that the bible on the floor is clearly open at different pages.
If the bible was put in the position in which it appears in the photographs by Jeremy Bamber, the blood stain on the carpet would have been still wet when he put it there. So it would have made a stain at different pages where it was open, not the ones where we see the stains.
Caroline's point as I understand it is that the blood must have been already dry when it was put there, otherwise there would have been an independent stain on the the left side page as opposed to faint mirror stains. But taking into account Myster's argument, there would have to have been stained pages we have never been shown, that is stains on the pages at which the bible on the floor is open at in the crime scene photographs.

In the above photograph, you can see that the bible is partly covering the stain on the carpet. It looks like it was put there when the blood was dry. The top of the pages where the bible is resting don't appear to be stained at all. But if there are other stained pages why have the police not disclosed the fact.
The bible must have been put there by the police when the blood was dry.