Re: Why do fruits resemble both parents?

Really there are two questions asked here.  One you already answer 
correctly, and to answer the other I'd need more information (data).  You 
are correct in understanding that the fruit is maternal tissue and only the 
seeds are hybrid offspring, so if two varieties of different fruit types 
cross pollinate, the observed fruit containing the hybrid seed would be 
fruits of the maternal type.  OK, now why don't you observe this?  First, 
remember that your garden seed are probably hybrids.  My best guess is that 
some of your seed are an F2 hybrid (usually you plant F1 hybrids for 
their uniformity) and therefore showing a hybrid fruit type.  If all the 
fruits on that plant are identical, this would pretty much confirm it 
because you would not expect all fruit to be caused by outcrossed 
pollinations.  Also, the immature fruits, the ovary below the corolla may 
have the characteristic hybrid fruit shape even before pollination, again 
pretty much confirming that you have some F2 hybrid plants.  Another 
approach would be to cross-pollinate by hand two different varieties to see 
if it affects fruit form.  This is of course why even Mendelian patterns of 
inheritance were not figured out until precise data was gathered and test 
crosses made. Sometimes we must investigate to obtain accurate answers.  
Sounds like your squash garden will be a busy place.