TJ, I have no specific knowledge on the subject of what might might have been left to be done for the Celestial AI LighBar however the Vanguard announcement identifies the following:

Poet Technologies and Vanguard Automation will initially collaborate to integrate the microlenses on Poet's LightBar products, aimed at AI (artificial intelligence)-ML (machine learning) accelerators and bio-sensing applications to validate power efficiency improvements and the viability of chip-scale, wafer-level manufacturing using microlenses. Poet expects to start sampling LightBar products incorporating Vanguard Automation's microlenses to customers in the second half of 2023.

Since POET already achieves excellent insertion efficiencies without active alignment the microlense feature is intended to ensure maximum yield across all optical engines. It will allow alignment tolerances to be relaxed. 

I understand that POET was also working on gratings which can add a number of functions to the platform but I would be speculating that this is required for the lightbar that POET is building for Celestial. Grating development would not really be something that would be challenging since they are widely used in photonics for top insertion at a given wavelength.