In SAP S/4HANA Cloud Public Edition, the characteristic that controls whether an asset is under construction is the 'Asset class'. Asset classes are used to categorize assets and define the controlling parameters for asset postings, including whether the asset is under construction. Assets under construction are typically managed in their own asset class with specific configurations, such as capitalization date rules and depreciation keys, tailored to the treatment of construction in progress until they are ready to be capitalized and put into use.
References:
SAP S/4HANA Cloud Asset Management guide
SAP Help documentation on asset classes and assets under construction