There could be a host of reasons, newt. Certainly it's a board from a different tree. The most likely explanation is that the light board came from a combination of some of the following reasons, or perhaps all of them. It is a different oak type, grown in a quite different climate, or different soil conditions to those experienced by the trees that provided the other planks. The term European oak covers a multitude of sins. Taxonomists can't even agree on how many oaks variants there are in the world, but it's generally agreed that there are between 250 and 450.
Oaks are notorious for cross fertilising and hybridising backwards and forwards. Quercus robur European oak (aka English oak if it's grown in the UK) is a pedunculate oak and will cross breed freely with Sessile oak Quercus patraea. A peduncle is a stalk and sessile means without a stalk. In fact, quite distantly related oaks are notorious for cross breeding freely, which explains in many ways oaks huge success as a species. It's a mongrel species that's adaptable through it's lack of genetic specialism and has an ability to cope with vastly different conditions from very hot to very cold, for instance.
Just yesterday I was adding some information to a text I'm working on about timber technology and, in this case, I was writing about this specific subject. I'd spotted two oaks growing side by side, but they were obviously different. One had most of the characteristics of the classic European oak, even down to the auricles found at the base of the dull green roughly round lobed leaves, yet the acorns were sessile-- they should have been pedunculate. So is the tree a Quercus robur or not? I think it's likely a Quercus robur cross with a Sessile oak.
The tree next door was obviously an oak, but it had sawtooth edged rather slender leaves with a shiny waxiness about them. The branches of this tree tended to hang down towards the ground more than the other tree which had the classic English oak look of branches twisting off at crazy angles. I was reminded almost of the evergreen Live oaks (Quercus virginiana) seen in south-eastern USA with Spanish moss hanging off the branches. I'm pretty sure this second oak is not an evergreen oak but that it's a white oak of some sort as is the first tree.
The point I'm getting to is that if both trees were harvested for their timber they'd probably be processed at the same time and the planks would get mixed up into one big pile with a load of other oaks. As timber they'd have many of the classical white oak features such as the prominent radial figuring seen in radially sawn boards, but their weight per cubic foot could be quite different, and there might be quite subtle but fairly obvious variations in the grain, the density, the colour, etc..
That's probably a lot more useless drivel than you wanted to read, ha, ha. Slainte.