Is 80cm of gravel needed under a 25cm thick concrete slab for frost protection?

Thank you so far for the numerous feedbacks, I am now in discussion again with the geotechnical engineer about what exactly needs to be done. If interested, I am happy to provide feedback again on what ultimately came out of it.

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Our neighbor across the street built a similar house with only 20cm of gravel. Is an 80cm gravel layer necessary or can the slab be otherwise protected against frost?
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The soil can look completely different just 5m away, so one should say goodbye to "But the neighbor has..." when it comes to foundations... maybe the neighbor just did a poor job or does your neighbor even know his soil survey? My neighbors certainly don't know theirs ;)

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For example, we have a 1.00m frost apron and on one side 1.00m of gravel and on the other side 0.20cm of gravel. It simply depends on the soil conditions... the ground engineer then decides based on experience.

One can only hope that the ground engineer sticks to the specifications from the geologist and the structural engineer and does not decide based on experience...

One can only hope that the civil engineer follows the specifications from the geologist and the structural engineer and does not decide based on experience...

Our general contractor is already strict when it comes to material and plate load test pressure. We had excellent values. There was a large clayey area on one side, which is visually noticeable. That’s why I mentioned experience. It was also stated that way in the report with the different levels. The civil engineer even removed more soil than recommended in the report. Although we gave away our soil and had no disposal costs, the bill was €20,000, twice as high as the estimate based on the soil report. This just shows again that civil engineering is a surprise package.