Certain cases are studied in which quantum dots (QDs) show no collective properties. It is demonstrated that physically isolated QDs (IQDs) are typical of the single-layer metastable QD arrays grown by submonolayer migration enhanced epitaxy on vicinal substrates. Their formation is attributed to the isolation of separate InAs clusters on vicinal terraces due to the wetting layer ruptures on the edges of bunched multiatomic steps. The carrier exchange between such QDs is not observed. Coalesced QDs formed in upper layers are typical of multi-layer metastable arrays. The lateral carrier exchange between such QDs is inhibited up to 300 K due to the effective electron channelling from them to underlying layers. It is demonstrated that the appearance of such isolated conglomerates results in the anomalous temperature dependence of photoluminescence (PL) for the multi-layer array. A model is proposed, which explains the influence of IQDs on the 3D array PL.