Two situations must remain distinct:
1. The sale itself stipulates that the fruit must stay on the tree until maturity.
2. After an otherwise valid unconditional sale, the tree owner separately permits temporary retention.
The first is a stipulation of retention and is condemned by Quduri. The second has its own discussion in Hanafi commentaries; it should not be equated automatically with a defective term of sale.
The duration, additional growth and possible withdrawal of permission require case-specific legal analysis, not an unconditional shortcut.