Fluid vacuum yields exact solutions to Pioneer anomaly and Mercury's perihelion (2019)

I have always understood that 'Mercury’s perihelion precession' is explained by Albert Einstein's General Theory of Relativity (GTR). The article suggest an alternative explanation, which seems to imply that the GTR is not true. The GTR already has been well established through the observation of many other physical phenomena. Which seems to nullify the alternative explanation provided by the article.

"Physical vacuum as a dilatant fluid yields exact solutions to Pioneer anomaly and Mercury’s perihelion precession" (2019) https://cdnsciencepub.com/doi/10.1139/cjp-2018-0744