Are these fruit flies really coming back to life after being frozen?
Short answer
Short-term freezing kills fruit flies. Long-term cryo-preservation of D. melanogaster is also not possible.  

Background
Per a publication of Koštál et al. (2016), long term preservation of insects is only possible for embryos, or larvae in diapause. Indeed, freezing is an effective way to kill adult fruit flies (source: Phys.org)

However, D. melanogaster adults show very weak capacity to enter reproductive diapause, and larvae possess absolutely no capacity for diapause Koštál et al., 2016).  

Reference
Koštál et al., Scientific Reports (2026); 6: 32346