There is not much info about it but I wouldn't assume that it is majorly harmful to guinea pigs.
We recommend to limit any pellets to 1 tablespoon per piggy per day. Pellets are the one part of the diet that can be dropped if you would rather replace them with fresh and dry forage instead. Fresh veg and pellets basically replace the supplementary role to the fresh grass/hay that are the mainstay of the diet. Even no added calcium pellets still contain more calcium weight per weight than the veg highest in it (kale).
Long Term Balanced General And Special Needs Guinea Pig Diets (includes information links to forage)