Contractor cut joists short (followup to earlier question)
I think the joists cut short are fine because, 1) required bearing is satisfactory, 2) withdrawal out of hanger is not of concern. 

1) Your 2x10’s at 16” on center spanning 12’ will support a maximum of between 100 per linear foot (plf) and 155 plf depending on the species and grade of the lumber. Therefore, the maximum load on each hanger is: 

155 plf x 6’ = 930 lbs.

Lumber can withstand between 375 psi and 455 psi in compression perpendicular to grain before it starts to crush. Therefore, the MINIMUM bearing length required in each hanger is:

930 lbs. / 375 psi x 1.5” (width of joist) =
1.6” into hanger 

The joists cut short at the top of the hanger is not important...there is no load on that portion of the joists, except to provide support for your subfloor. 

2) Withdrawal out of the hanger is not supported by the side nails, but rather by the subfloor. That is to say, the joists cannot “move” out of the hangers because they are secured in place by the nailing of the subfloor into each joists. 

Summary:
If the joists extend about 1 5/8” into the hangers, they can support the maximum load that a 2x10 joist at 16” on center spanning 12’ can support.