I just discovered that vips_sharpen requires band format VIPS_FORMAT_SHORT, but why does vips_sharpen itself not perform a conversion?

In my case, the saturation was adjusted by adjusting the AB values of LABS. As that correction was applied by VImage.linear({1, 1.1, 1.1}, 0) then the resulting LABS image became floats (I guess). When the sharpen was applied, an error was raised:

sharpen: image must be VIPS_FORMAT_SHORT

I found this check came from:

My pseudo code is:

auto img = img.linear({1, 1.1, 1.1}, 0);
img = img.sharpen(VImage::option()->
					set("sigma", 3 / 4.0)->
					set("x1", 2)->
					set("y2", 10)->
					set("y3", 20)->
					set("m1", 0.5)->
					set("m2", 1));

I can of course apply a cast, but why does vips_sharpen itself not apply a cast for an image that is already in LABS color space?