That is not part of the last update, only log-axis tick labels are affected, because they can be handled automatically by a specific log tick label formatter without requiring any intervention or special syntax from the user. “Math” text in more general text contexts (i.e. with LaTeX syntax) is part of the ongoing funded work (just now getting started) that is part of the grant the project received from CZI: Bokeh Receives CZI Grant
EditL For a more recent, technical, and lively discussion see also: Latex axis and title labels · Issue #6031 · bokeh/bokeh · GitHub