Question: Inconsistent(?) Dataframe indexing

Background

This 'quirk' of Maple behaviour cropped up when I was considering solutions for the question posted here

https://www.mapleprimes.com/questions/232433-Extract-From-Record

where the OP had "poorly structured" data which meant it was a bit "awkward" to access required fields. A number of more-or-less satisfactory solution were proposed, and the OP seems happy

The Issue

One possible way to solve the original problem would be to restructure the data as a DataFrame. The "natural" way to do this would be to use numeric row indexes.. Note that these row indexes are not contiguous, and are in no particular order. However using this approach means that accessing fields from the dataframe is not consistent.

Sometimes the supplied row label is interpreted as a 'label', sometimes it is interpreted as the "row number". It appears that the latter interpretation is preferentially used

I can't make up my mind whether to call this a "bug" or not, but I can see the inconsistent interpretation resulting in chaos.

Before submitting an SCR I'd like to know if anyone else sees this as a bug

Consider the code

  restart;
  prettyprint=1:
#
# data
#
  S := [`206` = Record(mu = 508.001018040,  sigma = 125.002863204708),
          `4` = Record(mu = 1008.001018040, sigma = 167.707232430134),
          `2` = Record(mu = 1208.001018040, sigma = 141.512246146314),
          `5` = Record(mu = 808.001018040,  sigma = 117.156800098735)
       ]:
#
# Construct the above as a dataframe - note row labels are numbers!
#
  DF:= DataFrame( Matrix([seq( [rhs(j):-mu, rhs(j):-sigma], j in S)]),
                  rows= [seq( parse( lhs(j) ), j in S)],
                  columns=[mu, sigma]
              );
  DF[206, mu];
  DF[2, mu];  ## Errr No!
  DF[5, sigma];
               [           mu             sigma      ]
               [                                     ]
               [206  508.001018040   125.002863204708]
               [                                     ]
         DF := [ 4   1008.001018040  167.707232430134]
               [                                     ]
               [ 2   1208.001018040  141.512246146314]
               [                                     ]
               [ 5   808.001018040   117.156800098735]

                         508.001018040

                         1008.001018040

                        117.156800098735

Note that DF[2, mu] outputs the entry from the second row - not the one from the row labelled with the number 2

I imagina a similar issue would occur with numeric column indexes, although I haven't tried this