Why is space inserted at beginning of table or figure caption when using macros to define caption label?

Question

Here is my MWE. As you can see, the problem only happens when we use the macro \suppOrApp.

\documentclass{article}

\usepackage[english]{babel}
\usepackage{blindtext}

\usepackage{caption}
\usepackage{float}
\usepackage{ifthen}

\title{A caption test}
\author{Some one}
\date{\today}


\begin{document}

\newcommand{\suppOrApp}{
  \ifthenelse{\boolean{thesisStyle}}
    {Appendix}
    {Supplementary}
}
\newboolean{thesisStyle}
\setboolean{thesisStyle}{false} % Might want to reconsider this here.


% This has additional space:
\renewcommand{\tablename}{\textbf{\suppOrApp Table}}
% But this would work fine.
%\renewcommand{\tablename}{\textbf{Supporting Table}}


\begin{table}
\begin{tabular}{cc}
1 & 2 \\
3 & 4 \\
\end{tabular}
\caption{\blindtext}
\label{mytable}
\end{table}

\blindtext

Please refer to Supporting Table~\ref{mytable}.

\end{document}