FTC’s diff algo also plays games with multipool “profitability” calculations as well, depending on sample timing. Can see this on whattomine, FTC is up one minute and down the next.
Yes, that is EHRC at work.
What the big coin switching pools do is also called ‘selfish mining’ as they throw in high hash power, mine a lot of coins compared to the ‘permanent miners’ and switch away, leaving the permanent miners with a low hash rate and high difficulty and less coins mined than they normally would with a constant hash rate.
EHRC was designed to react fast on changes in hash rate, driving away the coin switching pool shortly after they switch on and also adjust the difficulty down fast, so the loss of income for the ‘permanent miners’ is mitigated.