The x stretch block is a reporter block in the Looks category that reports the value of the x stretch, or the stretch of the sprite horizontally. By default, the value of x stretch is 100, which is also the default value in the set stretch to x: () y: () block.

Workaround

This block can be worked around by using a variable to save the x stretch when the set stretch to x: () y: () block is used:

when gf clicked
set [x stretch v] to [100]
define set stretch to x: (xPos) y: (yPos)
set stretch to x: (xPos) y: (yPos)::looks
set [x stretch v] to (xPos)

However, this workaround would need checks to make sure valid numbers are inputted if there is a possibility for invalid inputs in the code. set stretch to x: () y: () custom block would be used in place of the actual block in places other than the define block code.
A similar workaround can also be done for the y stretch block.

See also