Some added speculation...

Shash had indicated Finisar uses Si based, not GaAs, so likely no chance POET tech involved:

https://agoracom.com/ir/POETTechnologies/forums/discussion/topics/702005-this-is-an-opinion-ii/messages/2180354#message

Now, Finisar is completely refurbishing a shuttered plant in Texas, all new equipment, infrastructure, etc. to service Apple's needs, but are delayed in getting things into production due to a change in manufacturing process.  So, what's the nature of the change: is this just a tweaking of traditional process for their latest gen VCSEL or maybe challenge with volume; or, adoption of a new process they are much less familiar with, so experiencing some technical issues?

Shash's post makes sense, and seems a likely or most likely scenario.  However, if someone is picking up much of the tab to get you up and running, change may not be that risky.  Especially if the new tech is superior and you have a guaranteed pipeline into the fruit co.  Could be Apple secretly developed their own tech, or someone else has for them.  Only time will tell.