It was observed that in most methods in 310 and in the JDK the names of methods use "millis" and not "milli". See Clock, Duration, etc for examples.
Rename toEpochMilli and ofEpochMilli to use the plural.
This was deliberate. We also have LocalDate.ofEpochDay, LocalTime.ofNanoOfDay, LocalTime.ofSecondOfDay, LocalDateTime.ofEpochSecond and Instant.ofEpochSecond.
In general, we use singular for fields and plural for units.
I don't overly mind changing, but we'd have to identify every last case that needs changing for consistency.
The motivation to change is not compelling and it would cause other changes. The current approach is self consistent and deliberate. Leave it as is.