Is there a reason

Layout

composable function has

content

parameter first and not last, so it would allow for container-like invocation?

You can specify the parameters in whatever order you want if you name them

but that forces to specify all names except content one to get the container invocation

I can’t invoke it like

Layout(measureBlocks) { … }

in named parameters form

yes, the intended usage here is for implementing a custom layout composable, e.g.:

@Composable fun MyLayout(
  modifier: Modifier = Modifier,
  content: @Composable () -> Unit
) = Layout(content, modifier) { measurables, constraints ->
  // measure logic here
  layout(myWidth, myHeight) {
    // placement logic here
  }
}