The question is its relationship to plant roots. The term mycorrhizal is becoming almost meaningless in the broadness of its use. All soil microbes more or less have a relationship to plant roots. The rhizosphere is where everything happens in the soil. Soil bacteria, including Pseudomonas fluorescens, cluster around plant roots, because nutrients accumulate over time in that area.
Roots promote that result, since they benefit from the accumulation of nitrogen.
This result is not the same as that of true mycorrhizal fungi. The observed result with Morchella was clumping around large roots rather than an association with fine roots. If one therefore chooses to refer to Morchella as mycorrhizal, which is arbitrary, doing so tells nothing about the biology involved. It certainly does not lead to additional conclusions in regard to nutrition or plant specificity. Certainly plant roots are not required for the growth or nutrition of Morchella , since it grows readily in various composts.