[Tex/LaTex] Computer Modern Bold SF has rounded corners

Question

When experimenting with the Beamer class I noticed that when using the default SF font (which is Computer Modern AFAIK) in boldface the corners are rounded. It looks like completely different font. (And I think it is. Look at the shape of the 'o' (oh) which became squared instead of rounded.) I have never seen this before on fonts: bold is usually a bold version of the original font. Is this normal/intentional? Why?

I am creating a template for a presentation in company style so I am not allowed to change the font.

Compare Helvetica in normal and boldface, and compare Computer Modern Sans in normal and boldface.

\documentclass{article}
\renewcommand{\familydefault}{\sfdefault}
\usepackage{helvet}
\begin{document}
Helvetica\par
\textbf{Helvetica}
\end{document}

\documentclass{article}
\renewcommand{\familydefault}{\sfdefault}
%\usepackage{helvet}
\begin{document}
Computer Modern\par
\textbf {Computer Modern}
\end{document}

On a side note, for this post I had to create two documents. For the life of it, I have not been able to change the font back to Computer Modern Sans. Although I set the document default to Sans, this command would show Computer Modern with serif. Only when I comment out \usepackage{helvet} I can get the Computer Modern font.

\documentclass{article}
\renewcommand{\familydefault}{\sfdefault}
\usepackage{helvet}
\begin{document}
Helvetica\par
\fontfamily{cmr}\selectfont
Expected Computer Modern Sans here
\end{document}

Answer 1

Font design is the choice of the font designer.

But regarding the font change: You need to use cmss instead of cmr if you want the computer modern sans font:

\documentclass{article}
\renewcommand{\familydefault}{\sfdefault}
\usepackage{helvet}
\begin{document}
Helvetica\par
\fontfamily{cmss}\selectfont
Expected Computer Modern Sans here
\end{document}