It's hard to know the reason for which they sent this email.
Maybe they would like to know the reason for which some people buy a lot of Playmobil. Perhaps, they want to have a knowledge of the number of Playmobil collectors. For them, if you buy a lot, it certainely means that you are a collector. But they want to have a proove to indicate in their database the new status of official "COLLECTOR" ... I doubt that they wil give a discount to the collector.....In the mail sent you can read "These pictures and a hint "collector" will be added to your customer database."
In France, store is not allowed to refuse to sell something, what ever the quantity is. For example, if i want to buy 1000 playmobil soldier at Playmobil France, they will have to sell them, they can ask why! But they have to sell them, except if they are out of stock....even in that case they have to provie you with similar or more expensive item...as long as it is not written "limited quantity per order" it means that you buy the quantity you want.
The problem they can have with "huge" quantity of order, is the shipping cost. In France it's something like 6€....So if you order 50kg of Playmobil it will cost them more than 6€....so they lost money......