From my own experience as a banker, I find the approach completely acceptable. Sorry for that
Many banks make it quite easy for themselves here. A common phrase points out that in the event of insolvency, a forced auction (well, or a "distressed sale") would have to be conducted and the proceeds achieved here would be lower than in a regular sale.
§ 3 of the BelWertV (Ordinance on the Determination of the Mortgage Lending Value) actually sets out the calculation principles:
(1) The value underlying the lending (mortgage lending value) is the value of the property that can be expected, based on experience, to be achieved on the relevant land market independently of temporary, e.g. cyclical value fluctuations and excluding speculative elements, over the entire term of the loan
in a sale.
(2) To determine the mortgage lending value, the
future marketability of the property shall be taken into account on the basis of the long-term, sustainable characteristics of the object, normal regional market conditions as well as current and possible alternative uses within the framework of a cautious valuation.
This is often implemented very restrictively in the written regulations (e.g. organizational instructions etc.) (primarily applies to covered bond banks). Here, very significant discounts are often applied (also allegedly for security reasons). Other factors to reduce the actual market value are also all too willingly used, e.g. significant parts are not building land.
In fact, the circumstances of the individual case should be taken into account and the object should be valued with regard to its future marketability. If it concerns desirable locations and plot sizes and the forecast for possible future utilization is positive, this can and should lead to a proper valuation. If the location is rather modest, the purchase price may already have been high overall. If the utilization forecast is negative, this will generally result in a fairly low mortgage lending value (necessarily).
The banks have a legitimate interest in security but often overload the appraisals with (improperly) high discounts.
Conclusion: A factual consideration of the basics of valuation and obtaining competing offers also repeatedly lead to an adjustment upwards of the pessimistic view. Now the assembled banker colleagues will probably pounce on me (me, the filthy informer).