Mega Evolving is optional in battle meaning Feraligatr gets the best of single typing and duel typing depending on the situation in battle. Mega Evolution isnt permanent, unless thats something new they added. If you realize that Dragon would be a bad type during a matchup, then just dont Mega Evolve. Ppl been using Tera forms and they pretty much the same kinda tech strategy, change typing in battle. Mega normally just has better stats but if you add a type, thats just a bonus.