The on-line movie behind the figure shows the migration before and after amplitude gain with time. You can get a bad result if you gain up the data, say with automatic gain or with t2, for display before doing the migration. What happens is that the hyperbola flanks are then included incorrectly with too much strength.
The proper approach is to gain it first with which converts it from 3-D wavefields to 2-D. Then migrate it with a 2-D migration like kirchfast(), and finally gain it further for display (because deep reflectors are usually weaker).
1