Are people sloppy with the partial symbol?

Suppose y = f(x,y,z) where x and y are independent but z = x^2 say.

Then dy/dz = @f/@x dx/dz + @f/@y dy/dz + @f/@x

but do people sometimes still write this as @y/@z?

Even though z is dependent upon x, @y/@z means that that x and y are
held constant, but x is allowed to vary in the z terms, correct?

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