Node text baseline in tikz for multi-part-nodes

Question

I basically have the exact same problem as this question, only for multi-part nodes: I have a node that consists of 3 parts, each of which contains text. I want to have the text aligned by its baseline. I tried to achive this using the text height and text depth, which works fine for ordinary nodes, but not for multi-part ones. As you can see in the image below, only the first part of the node receives the correct alignment I want to achieve, the other two get "push up" by characters that extend below the baseline.

This is my latex-code:

\documentclass[tikz, 11pt,landscape]{article}

\usepackage[default,osfigures,scale=0.95]{opensans}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{tgbonum}
\usepackage{tikz}
\usetikzlibrary{shapes}
\usetikzlibrary{calc}
\usetikzlibrary{arrows.meta}

\usepackage[a3paper]{geometry}

\begin{document}
\thispagestyle{empty}

\tikzset{normal/.style = {rectangle split, rectangle split horizontal, rectangle split parts=3, very thick, draw=black, minimum height=0.6cm,text height=1.5ex, text depth=0.25ex}}

\begin{tikzpicture}[remember picture, overlay]
    \node[normal] at (current page.center) {\nodepart{one} ag \nodepart{two} ag \nodepart{three} ag};
\end{tikzpicture}    
\end{document}

I found another post about someone having the same problem with transparency only beeing applied to the first part, but its solution didn't work for me. I do not care about multi-line text and actually only really care about the alignment in the second part of the node, I just included the other two texts for demonstration. It seems like whatever I try, it only gets applied to the first part.

Edit:

Using my screenshot as an example: I want the 2nd and 3rd box to be aligned to the height of the 1st one. I do NOT want to align the 1st box to the height of the 2nd and 3rd one, since that is quite high and looks strange if I have a text without characters that go below the baseline. The spacing will look very uneven.

Answer 1

A lot of thanks to @CarlaTex kindness and to her explanations that make me understand ( I hope this time I am not wrong!) what is really needed by this question

The workaround is the use of an invisible \rule that has the correct vertical dimensions (height and depth):

\documentclass[tikz, 11pt,landscape]{article}

\usepackage[default,osfigures,scale=0.95]{opensans}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}

\usepackage{tgbonum}
\usepackage{tikz}
\usetikzlibrary{shapes}
\usetikzlibrary{calc}
\usetikzlibrary{arrows.meta}

\usepackage[a3paper]{geometry}

\begin{document}
\thispagestyle{empty}

\tikzset{
    normal/.style = {
       rectangle split, 
       rectangle split horizontal, 
       rectangle split parts=3, 
       very thick, draw=black, 
       minimum height=2cm,
       text height=1.5cm, 
       text depth=0.25cm
                    }
        }

\begin{tikzpicture}[remember picture, overlay]
    \node[normal] at (current page.center) {\nodepart{one} ag 
            \nodepart{two} \rule[-0.25cm]{0pt}{1.75cm}ag 
             \nodepart{three} \rule[-0.25cm]{0pt}{1.75cm}ag};
\end{tikzpicture}    
\end{document}