INTERPRET REGRESSION RESULTS MATLAB

I have a question regarding interpretation of results using stepwise function to perform regression; If I run regression model using mdl= stepwiselm(X,y,'quadratic'), and the model returns in the form; y ~ 1 + x1*x2 + x1^2 +x2^2; Without showing the SE, t-Stat & pValue columns etc, the output I get is along the lines of;

                     Estimate           
                     ________        
 (Intercept)             Value (A)      
  x1                   Value (B)       
  x2                  Value (C)        
  x1:x2              Value (D), for the x1*x2 term in model         
  x1^2              Value(E), for the x1^1 term in model         
  x2^2             Value(F), for the x^1 term in model

Am I correct to interpret that the output values associated with x1 & x2 term are represented only because they are lower order terms of the x1^2 & x2^2 terms, they are not stand alone terms to be used with the model?

i.e; my model would be y ~ A + D*x1*x2 + E*x1^2 +F*x2^2); or;

 y ~ A + D*x1*x2 + B*E*x1^2 + C*F*x2^2;??