Bootstrapped distribution of $l_v^{\ast }$ for the axisymmetric NSD model without (blue) and with (red) the observational selection function applied. Each distribution results from 10 000 bootstrap iterations sampling N = 12500 stars from the region |ℓ| < 0.9° and |b| < 0.25°. The unbiased NSD yields l_v = (−87.4 ± 5.2)°, consistent with an axisymmetric disc. However, applying realistic selection effects shifts the measurement to l_v = (82.2 ± 5.1)° (towards positive values), demonstrating that observational biases could mimic a nuclear bar with its near side at negative longitudes if not properly corrected.