If I’m not mistaken, subtracting dict.items() would try to remove duplicated entries as seen here:
d1 = {'a': 1, 'b': 2, 'c': 10}
d2 = {'a': 3, 'b': 4}
print(d1.items() - d2.items())
> {('a', 1), ('b', 2), ('c', 10)}

d1 = {'a': 1, 'b': 2, 'c': 10}
d2 = {'a': 3, 'b': 4, 'c': 10}
print(d1.items() - d2.items())
> {('a', 1), ('b', 2)}

so compare the values via:
model = models.resnet50(pretrained=True)
model.eval()

stateDict = model.state_dict()
torch.save(model.state_dict(), 'test.pth')
reloadDict = torch.load('test.pth')

diff = stateDict.items() - reloadDict.items()
len(diff)

for key in stateDict:
    paramA = stateDict[key]
    paramB = reloadDict[key]
    print(key, (paramA - paramB).abs().max())

which will show a zero difference.