We currently split batches after ferment - roughly half to BBT for kegging, the rest gets bulk primed in the FV and bottled.

All our bottle conditioned stock ends up dropping very clear (with sediment on the bottom of course).
The portion sent to the BBT won't clear. A few days in the BBT under pressure sees it clear a little but still very much a Hefe, whereas the bottles are Krystal.

The beer gets a dose of Biofine Clear in FV before splitting.
Usually held at 4°C if splitting the batch, but our latest went all to kegs and even though we held it at -1°C for a week, it didn't clear much.

Any ideas on whether this is a pressure vs time issue, or is there some magic happening during the 2nd ferment?

This only happens with our wheat beer - all others clear very well after biofine.

Grist is 50:50 Wheat Malt:Pale Ale Malt + Fermentis WB-06