Tofu possesses a more complete amino acid profile than most plant-based proteins but has lower amino acid bioavailability than animal-derived proteins such as eggs, meat, and dairy.

Study: Probiotic Administration Increases Amino Acid Absorption from Plant Protein: a Placebo-Controlled, Randomized, Double-Blind, Multicenter, Crossover Study

This study shows that the body doesn’t absorb amino acids as well from plant proteins like pea as it does from animal proteins like eggs or meat. Since tofu is also a plant protein, this suggests the same is likely true for tofu — it has good amino acids but your body doesn’t absorb them as well as from animal sources.

Study: Effects of Consuming Ounce-Equivalent Portions of Animal- vs. Plant-Based Protein Foods, as Defined by the Dietary Guidelines for Americans on Essential Amino Acids Bioavailability in Young and Older Adults: Two Cross-Over Randomized Controlled Trials

This study found that your body gets more usable amino acids from eggs and meat than from beans and nuts — and tofu is similar to beans and nuts, so it makes sense that your body absorbs less from tofu than from eggs or meat.

Study: True ileal amino acid digestibility and digestible indispensable amino acid scores (DIAASs) of plant-based protein foods.

Tofu has all the essential amino acids better than most plant foods, which is true. But the study shows your body absorbs almost as much protein from tofu as it does from eggs or meat — so it's not worse at absorbing, contrary to the claim.

Study: In vitro protein digestibility of different soy-based products: effects of microstructure, physico-chemical properties and protein aggregation.

Tofu has all the essential amino acids your body needs, better than most plant foods, but your body can't absorb them as well as it can from eggs or meat — this study shows tofu's proteins are harder to break down in the gut than some other soy foods.