Nope, that’s not what happened. I just checked again and I noticed two things:
(1) Although the warning (from epizy.com) said the account would be deleted in 2 days time, the post-deletion notification (from infinityfree.net) was dated 4 days later. I don’t know for sure when the deletion itself occurred, but if the post-deletion notification was sent on the same day as the deletion, then they may have allowed an extra two days grace before deleting the account, though even 4 days is still pretty short notice.
(2) The warning notice had a long link at the end, prefaced by the sentence:
“If you require this account re-activated, please click the following link”
On close inspection of the link, I found the correct account username, epiz_28412077, embedded in it, though the account name mentioned earlier in the email body and in the subject line was completely different in both format and content. That one was “account p4biohnr.epizy[dot]com”.
Also, I now see that the warning email contains the specific answer to my question: “Your … account has received less than 5 visitors in the past 30 day period.” It’s good to know in hindsight, but it would be appropriate for this minimum requirement to be specified where it actually belongs, i.e. in the terms of service, where, as I said previously, the only mention of an activity requirement merely says, “extended periods of inactivity” as one of the reasons listed for which Infinity Free may delete an account. It could (and, legally, probably should) be more informative as to what, specifically, is the required minimum activity.
@KangJL linked to a recent reply by Admin to a similar question asked by MaxiTrauma, and even that answer was similarly vague, saying “a few hits every month.” Do we have to guess what “a few” means? If the minimum is actually 5, then why not say so clearly so that new users can be properly informed of what the minimum requirement actually is?
Additionally, this requirement is not really within the ability of the site owner alone to comply with. I can’t control how many people visit my site or how often they visit, so it’s not a very fair choice of criterion for activity. Another well-known provider of free web-hosting requires site owners to login to their hosting account once a month. At least that is usually within an account holder’s control.