I have replaced it by keepCurrentZoomLevel: true. 
My suggestion is to use keepCurrentZoomLevel: true as a default feature (there is then no need to set maxZoom), and otherwise use maxZoom if you want to force a zoom level.

Maybe it would be more clear to use maxZoom and to set a value like maxZoom: 'keepCurrent'? (but then it is not consistent with your second comment below).

I am new to this project, so sorry if I don't understand quite well how it works and why it was designed in a certain way.