No matter from which region or country you are transferring from, including Germany and other European countries, the €100 buffer is mandatory. The buffer is meant to cover the unexpected expenses and fees that might take place.
For example, fluctuations in currency exchange rates, extra fees your bank takes for international transactions, etc. will affect the amount that arrives in your blocked account. The purpose of the buffer is to ensure that your funds will be still sufficient even if less arrives than what you intended.
By transferring the buffer together with the Blocked Amount you secure yourself and avoid the situation when unexpected fees and costs make the amount you transfer lower than the necessary amount for the creation of your Blocked Account. Thus, transferring a bit more at the very beginning can save you from the need to make a second transfer to cover up special bank/exchange fees later on.