The folks who write those blurbs for seed companies are rarely growers. They just pick up something they have read and dress it up to sound good. Eden's Gem is a relatively new name, never heard of it till recently. Have not tried it. Some companies claim it is the 20th century Rocky Ford Netted Gem which I have grown. That one is an improved version of the old Netted Gem from the 19th century. I have also grown this one. The Rocky Ford version is larger than the original but both are small melons. Neither is early, being main season 85-90 day class.
Ambrosia has 6 foot vines. I grow on 5 ft centers, but you pays your money and takes your choice. Higher plant densities are quite possible under ideal conditions.

Many companies take their maturity dates from the seed supplier/grower. I still haven't figured out exactly when/where these figures came from but I think many are dates for maturity where the seeds were bred and/or grown on for the seed packet trade. Many times this is California. Where I live in the cool Pacific NW those dates are way too early. Very few companies give longer dates though, for many reasons.

First, they sell to customers all over the country so maturity for a Florida gardener, or an Illinois gardener can and will be a lot different than for a Washington (where I live) gardener. If they list something as "90 days" they are going to be wrong depending on where the seed is planted or what season its planted in if its something like broccoli which can be grown spring, summer or fall.

Second, if a company in my area gave local maturity dates of say 90 days for Early Girl tomato vs. another company selling theirs listed with 55-60 day maturity (the "standard" usually seen) many people are going to go for the one listed with the shorter date. Not all gardeners are educated in this and they want the "earliest" corn, etc.

This said, most companies use the "industry standard" dates. This still allows you to compare one variety against another and choose which you want. It is then up to you, under this imperfect system, to educate yourself on how much longer you will have to wait for maturity given your climate. I say "how much longer" because we almost never get shorter maturity times than the packets. Despite being a far north state, with long summer days, we are cool, especially at night. A northern state that has a lot more heat, say Minnesota or New York, may be closer to the dates given on the packets.