Startparameters - Append to generated command?

[Jacksaur]

I want to add a single extra flag to my TF2 server's launch command (-unrestricted_maxplayers). As the docs say, the way to do this is to enter it under startparameters in the instance file.
However, this wipes out all parameters initially provided by the instance file, requiring me to do a ./tf2server details beforehand, to copy out and paste in the entire command used manually. Which also now makes the entries in my instance file useless and editing it a little more awkward.

Is this deliberate behaviour? Is there another setting I can use, that would just append additional parameters onto the existing command generated from the instance file entries?