I also thought about this but I think the following paragraph combined with minimum wage plus the fact that at early retirement you will have significant assets rule this out. What do you think?:
“Anyone with no income or only a low income is regarded as
non-employed. This includes in particular:
…
Insured persons who are not in permanent full-time work and whose contributions from gainful employment, including employer’s contributions, amount to less than half of what they would have to contribute as a non-employed person. Anyone who works for less than nine months a year or works less than 50 % of normal working hours is regarded as not being in permanent full-time employment.”