Ok cool. I found out how to do it properly. 
* Max resize to height, set to null for double textarea height or -1 for unlimited
* @type {int}
*/
resizeMaxHeight: null,
/**
* Max resize to width, set to null for double textarea width or -1 for unlimited
* @type {int}
*/
resizeMaxWidth: null,
/**
* If resizing by height is enabled
* @type {Boolean}
*/
resizeHeight: true,
/**
* If resizing by width is enabled
* @type {Boolean}
*/
resizeWidth: true,
Change to:
* Max resize to height, set to null for double textarea height or -1 for unlimited
* @type {int}
*/
resizeMaxHeight: -1,
/**
* Max resize to width, set to null for double textarea width or -1 for unlimited
* @type {int}
*/
resizeMaxWidth: null,
/**
* If resizing by height is enabled
* @type {Boolean}
*/
resizeHeight: true,
/**
* If resizing by width is enabled
* @type {Boolean}
*/
resizeWidth: false,
That doesn't set a fixed min-height equal to default height, but does stabilise the width and allow unlimited max-height.