In 2015 it had a stop sell. Presumably it was because high costs meant a low uptake, and also OpenReach were meant to be concentrating on the mainstream not the niche (link).
Actually, no. Demand was too high - BT couldn't cope.
It is clear to me that BT intended FTTPoD as part of their niche business offerings, not as a mainstream service. That put the work into the list of tasks allocated to their niche/business staff.
In putting the stop in place (at BT Wholesale), the inference was that BT Openreach was finding installation was taking much longer than expected, making it hard to achieve the FTTPoD installation work within the deadlines (something beyond 45 days, IIRC); this had a consequential impact on fulfilling the deadlines for "normal" (but still business/niche) ethernet products.
The choice to stop selling was said to allow the ethernet product delivery times to recover. BT's research side then used the time to come up with an alternative deployment method.
In April 2016 it was launched again (link)
It has been a strange launch, with very limited availability.
BT Research has come up with newer deployment method, both for native FTTP, and FTTPoD, but these methods don't seem to have been released into normal usage yet. These changes seem to get grouped alongside G.Fast under a banner of "NGA2".
The real driver for re-launch was probably that BT made some commitments with the "Superfast Cymru" group, as part of the BDUK subsidy programme, to make a certain amount of FTTP available in Wales. It appears that this commitment is being honoured through the FTTPoD product line.
It appears that BT's decision to reactivate FTTPoD, and make it more available, is mostly limited to exchanges in Wales, and Spectrum Internet's involvement is likewise limited.
The deployment method seems to remain as before, alongside (likely) slow installation times and high costs.
I suspect (with no evidence) that FTTPoD might become more widespread outside Wales as "NGA2" becomes more widespread - so linking it with the rollout of G.Fast. The existence of G.Fast products might then make FTTPoD even more niche than before (so BT can handle the lower number of orders). The newer deployment method might make it cheaper.