My citations should be in the format Author et al., 20xx. I understand from prior answers that it maybe because it is the first time citing a multiauthored manuscript in my text, but I don't see risks of ambiguity here in going with the et al. since the very first citation.
\documentclass{article}
\usepackage[backend=biber, style= authoryear-icomp,
dashed=false,
citestyle=apa,
maxbibnames=1,maxcitenames=1,uniquelist=false,
sorting = nyt, natbib]{biblatex}
\DeclareLanguageMapping{american}{american-apa}
\addbibresource{sample.bib} %Imports bibliography file
\begin{document}
\section{First section}
Items that are cited: \textit{The \LaTeX\ Companion} book \cite{latexcompanion}, The Einstein's journal paper \cite{einstein} and the Dirac's book \parencite{einstein, einstein1} are physics related items. Next, a citation about \textit{The \LaTeX\ Companion} book \cite{latexcompanion}.
\medskip
\printbibliography
\end{document}
simple.bib
@article{einstein,
author = "Albert Einstein",
title = "{Zur Elektrodynamik bewegter K{\"o}rper}. ({German})
[{On} the electrodynamics of moving bodies]",
journal = "Annalen der Physik",
volume = "322",
number = "10",
pages = "891--921",
year = "1905",
DOI = "http://dx.doi.org/10.1002/andp.19053221004",
keywords = "physics"
}
@article{einstein1,
author = "Albert Einstein",
title = "{Zur Elektrodynamik bewegter K{\"o}rper}. ({German})
[{On} the electrodynamics of moving bodies]",
journal = "Annalen der Physik",
volume = "322",
number = "10",
pages = "891--921",
year = "1905",
DOI = "http://dx.doi.org/10.1002/andp.19053221004",
keywords = "physics"
}
@book{dirac,
title={The Principles of Quantum Mechanics},
author={Paul Adrien Maurice Dirac},
isbn={9780198520115},
series={International series of monographs on physics},
year={1981},
publisher={Clarendon Press},
keywords = {physics}
}
@book{latexcompanion,
author = "Michel Goossens and Frank Mittelbach and Alexander Samarin",
title = "The \LaTeX\ Companion",
year = "1993",
publisher = "Addison-Wesley",
address = "Reading, Massachusetts",
keywords = "latex"
}
@online{knuthwebsite,
author = "Donald Knuth",
title = "Knuth: Computers and Typesetting",
url = "http://www-cs-faculty.stanford.edu/~uno/abcde.html",
keywords = "latex,knuth"
}
@inbook{knuth-fa,
author = "Donald E. Knuth",
title = "Fundamental Algorithms",
publisher = "Addison-Wesley",
year = "1973",
chapter = "1.2",
keywords = "knuth,programming"
}
@book{knuth-acp,
author = "Donald E. Knuth",
publisher = "Addison-Wesley",
title = "The Art of Computer Programming",
series = "Four volumes",
year = "1968",
note = "Seven volumes planned",
keywords = "knuth,programming"
}
@article{ctan,
author = "George D. Greenwade",
title = "The {C}omprehensive {T}ex {A}rchive {N}etwork ({CTAN})",
year = "1993",
journal = "TUGBoat",
volume = "14",
number = "3",
pages = "342--351",
keywords = "latex"
}



apastyle has quite strict rules for citing multiple authors. It's not intended as a style whose behaviour is designed to be modified. It might be better to use one of the standardauthoryearstyles instead. – Alan Munn Jul 22 '19 at 03:47