Yes, it has. This may have inflated measured T levels in the past. Still the decline trend of 1% per year can be established even if looking at the past decade or so.

1960s–80s Radioimmunoassay (RIA) Lower specificity, cross-reactivity issues

1990s–2000s Improved RIA and early mass spectrometry (MS) Moderate accuracy

2010s–Present Liquid chromatography–mass spectrometry (LC-MS/MS) Gold standard: high precision & specificity