In this preprint, Beyers et al. use ligands of both HaloTag and streptavidin to control protein–protein interactions. The approach is interesting, but at least two points need attention. 1. The evidence for Golgi-to-ER recycling of ManII is over-interpreted. The KDEL receptor is present throughout the Golgi and can retrieve KDEL-bearing proteins even from the trans-most cisternae (https://doi.org/10.1083/jcb.129.2.309). The return of ManII to the ER observed with BOLT may therefore reflect KDEL receptor–mediated retrieval of the KDEL-bearing complex, rather than the protein’s own recycling pathway. 2. Inducible and reversible control of the RUSH system has already been demonstrated The Introduction states that streptavidin–SBP binding is “virtually constitutive, prohibiting inducible interaction”, and this framing underpins the claim of novelty. Indeed, artificial ligands of streptavidin (ALiS) were developed specifically to make RUSH reversible and inducible (https://doi.org/10.1021/jacs.5b05672) and (https://doi.org/10.1002/cbic.201600640). ALiS allow bidirectional control of ManII transport, both ER-to-Golgi and Golgi-to-ER. These studies should be cited, and the novelty claims revised accordingly.