Google has removed the reference to 50 conversions required from its documentation on learning periods for bid strategies. The updated help page now only states that the calibration typically takes 1-2 conversion cycles, without mentioning a specific conversion count.
Previously, it suggested that up to 50 conversion events or 3 cycles might be needed.
Read the official help page here: Duration of the learning period for campaigns and what affects it.
This update was spotted by Hana Kobzová.