Interpretation of the soil survey report

There is no rainwater drain on our property; we have to let the water infiltrate on the site.

Then I would tend to go for a variant without drainage. That way you can't rely on the drainage working when it matters. In any case, with drainage you have the problem that it needs to be flushed regularly to function. At first you might do that, but probably not after 10 years.

Are you aware that these are two different alternative positions from one provider?
Besides, I have roughly summarized the items from the offer here for better readability.
So I don’t quite understand how you arrive at your corresponding conclusions...

Quite simply: it did not become clear to me that (1) and (2) refer to variants from the same bidder instead of offers from two bidders.

However, it remains that only one of the proposed approaches can be "more correct" and above all correspond to the same tender.

You have the expert report and have discussed it here. From this, a specialist planner should have a clear view of which measures are suitable or required here. If both offers were equivalent (whereby in that case the planner should have tendered both variants, not the bidder giving two answers to one question), then it must be the case that the reason for the drainage would have to lie buried in the deep layer "60 to 150 cm below finished ground level." Is it (yes or no, I would not want to literally rely on "maybe")?

By the way, a proper tender should include clear volume specifications here and corresponding additional quantity prices in the offer. Even the cm are unsuitable since the finished ground is not level, but the result must be.