Copying is never exact. The copied account fills a fraction of a second later, at a different queue spot, possibly with different size, so the copies drift from the source. Firms manage this by copying only traders whose style tolerates latency.
Traders also use copiers across several funded accounts, which concentrates risk: one bad idea breaches the daily-drawdown on every account simultaneously.
Example: a trader runs three $50,000 evaluations through a copier with a 3% daily loss limit. One trade goes 40 points against them on 2 contracts per account. All three accounts take a $4,000 loss at once, all three breach $1,500 daily limits, and all three are failed by the same click.
Related: live-funded-account, sim-funded-account, daily-drawdown, consistency-rule