Use tiny house as an extension or affordable extension options?

But that is not the case in every company.
In my husband's company, for example, it was specifically called mobile working, not HO, so that employees can work wherever they want.

That's the difference between mobile working and working from home.
By the way, employers usually do not offer mobile working instead of home office because they suddenly develop bouts of altruism.

In the home office, the employer must observe the workplace ordinance and monitor compliance (escape routes, lighting, ...). They do not have to do this with mobile working because the workplace is not fixed and therefore the inspection obligation cannot be fulfilled.

Additionally, the provision of equipment (office chair, desk, etc.) for employees is not a requirement in mobile working. The employer can simply hand the employees a laptop and say: Good luck, we are working mobile now!

For this reason, most companies prefer to offer mobile working instead of home office because it is simply cheaper and easier for them...

That's the difference between mobile work and working from home. Employers usually do not offer mobile work instead of working from home because they suddenly experience bouts of altruism.

When working from home, the employer must comply with the workplace ordinance and monitor compliance (escape routes, lighting, etc.). They do not have to do this with mobile work because the workplace is not fixed and therefore the inspection obligation cannot be fulfilled.

Additionally, providing furnishing items (office chair, desk, etc.) for employees is not a requirement for mobile work. The employer can simply hand employees a laptop and say: Good luck, we are working mobile now!"

Therefore, most companies prefer to offer mobile work instead of working from home because it is simply cheaper and easier for them...

It is also beneficial for both sides. Motivation is higher when you can work wherever you want.

Regardless, no one really checks where you actually work. Paper is patient.

That works fine until someone slips on ice on the way to the outbuilding. Then it will be looked at very closely whether it really is a work accident or not.
Apart from that... anyone who sits in the office all day wants living space standards, not a drafty garden shed.

For my husband, for example, it was called mobile working, not home office, so that employees can work wherever they want.

It’s called mobile working because the employer then gets rid of most regulations. The official workplace is still in the office, where the employer controls the conditions.

That works fine until someone slips on the way to the outbuilding due to black ice. Then it is looked at very closely whether it really is a workplace accident or not.
Aside from that... anyone who sits in an office all day wants living space standard and not a drafty garden shed

This was not about a drafty garden shed, but about a tiny house, which just officially cannot be called living space because in Germany we insist on overregulating everything down to the last detail.
Yes, and of course you can always look for the smallest flaw in everything, but you still cannot protect yourself from all dangers and eventualities. Often it is good to simply do something in a way that makes you feel comfortable.

But if you want to set up a Tiny House with about 50 sqm on your property, then the building regulations clearly apply, also for Tiny Houses.

The thing definitely requires approval. Bedrooms and offices are definitely living spaces, and at that size you exceed any exemption limit anyway. As living space, the house must comply with the Building Energy Act. The manufacturer promises something, but with 15cm insulation I am a bit skeptical. Prefabricated house manufacturers need significantly more; Danwood, for example, has 12cm Styrofoam plus mineral wool in the stud frame, if I remember correctly. Pineca promises to achieve that with about half the thickness, and at that price it is certainly not high-performance insulation. On the subject of airtightness and especially vapor barrier, I am also looking forward to the exact wall structure.