surprising conventions used for ProjDataInfoBlocksOnCylindricalNoArcCorr constructor and subsequent problems

I'm following the plot_scanner_LORs example

num_rings = scanner.get_num_rings()
num_dets_per_ring = scanner.get_num_detectors_per_ring()

#scanner.set_scanner_geometry("BlocksOnCylindrical")
#scanner.set_up()
# %% construct new span=1 data
# more complicated then it should be
min_r_diff = stir.IntVectorWithOffset((2 * num_rings - 1))
max_r_diff = stir.IntVectorWithOffset((2 * num_rings - 1))
num_ax_pps = stir.IntVectorWithOffset((2 * num_rings - 1))
for i in range(0, 2 * num_rings - 1, 1):
    min_r_diff[i] = -num_rings + 1 + i
    max_r_diff[i] = -num_rings + 1 + i
    if i < num_rings:
        num_ax_pps[i] = num_rings + min_r_diff[i]
    else:
        num_ax_pps[i] = num_rings - min_r_diff[i]
    # print(num_ax_pps[i])

proj_data_info_blocks = stir.ProjDataInfoBlocksOnCylindricalNoArcCorr(scanner, num_ax_pps, min_r_diff, max_r_diff,
                                                                      scanner.get_max_num_views(),
                                                                      scanner.get_max_num_non_arccorrected_bins())

Surprisingly, this gives min_segment_num=0, with the first segment corresponding to min_r_diff[0], as opposed to the usual "centred" approach, where segment_num range is symmetric.

This doesn't seem to cause problems, except for the VoxelsOnCartesianGrid constructor, which returns an image with only 1 plane

target = stir.FloatVoxelsOnCartesianGrid(proj_data_out.get_exam_info(), proj_data_out.get_proj_data_info(), zoom)

This is because that constructor uses segment 0 to find information
https://github.com/UCL/STIR/blob/4704b12cccb559866ab415152423e24258699b3d/src/buildblock/VoxelsOnCartesianGrid.cxx#L76-L78