Something to keep in mind, Baltic Birch is a hardwood, in it's own right. One of the species used to make BB plywood is Silver Birch, which has a Janka Scale rating of 1210, which is comparable in hardness to red oak, ash and beech. Sugar (hard) Maple has a janka scale rating of 1450, so the wood itself isn't even all that much softer than hard Maple. Couple that with the alternating grain pattern of the different layers and the glue and it's easy to see how it can he hard on blades.