FindPotentialStereo() doesn't find *marked* ring stereo when flagPossible=False

[greglandrum]

To Reproduce

In [48]: m = Chem.MolFromSmiles('C[C@H]1CC[C@H](C)CC1')

In [49]: for si in Chem.FindPotentialStereo(m,cleanIt=True,flagPossible=True):
    ...:     print(si.centeredOn,si.specified)
    ...: 
1 Specified
4 Specified

In [50]: m = Chem.MolFromSmiles('C[C@H]1CC[C@H](C)CC1')

In [51]: for si in Chem.FindPotentialStereo(m,cleanIt=True,flagPossible=False):
    ...:     print(si.centeredOn,si.specified)
    ...: 

In [52]: 

Expected behavior
both versions of the call should return the same results

Configuration (please complete the following information):

• RDKit version: 2021.03 and master
• OS: all