Not really, from 1-30 and heck even 1-50 and honestly certain jobs change distinctly from 50-60, so to suggest that playing the job from lv 1 somehow teaches you the job better is honestly inaccurate.
From NIN 30-50 you learn how to use jutsu and weave in huton for the reduction in skillspeed meanwhile once you hit 54 you learn a new 3 step combo closer that refreshes 30 seconds to your huton buff as long as it's active up to 70 seconds max changing the way you now use your jutsu to focus more on being pure offensive once you got the first huton off.
BRD/MCH change pretty drastically with their stationary stances forcing them to have to be aware of their position when they attack and to move out of AOE's as needed while potentially losing DPS out of it.
BLM gets 2 new abilities leylines which gives them an extra reason to stay stationary in the location of their choice and enochain which gives them a "huton" like aspect of upkeeping a buff that allows them to use Fire IV as long as they weave back and forth with Blizzard IV to keep Enochain up.
Basically a lot of jobs change the way they play from 50+ and most jobs don't even start til 30+ but even then with NIN it's just "shuriken" every 30 seconds til you get 35 and even then it's a choice between raiton single target or Katon aoe dmg, and with the changes to katon and it's damage potency there is even less thinking if you have least 3 mobs or more in the group.
Overall, it honestly isn't that hard to learn X job and even then, if people reallly want that slow pace of learning the job, just do POTD, yes you level up faster but quite honestly, it's way better to learn the job like that ina quick pace to get a slow ease of each skill then to press 1 til level 5 and then press 1-2 and sometimes 3 til level 10 and then sometimes press 4 but not until 20+ where you might be doing 1-2-3, 4-5 and then back to 1-2-3.
The complexity of the game isn't there at lower levels and it is just smarter for them to cut that unnecessary fat out when introducing a new job. Players aren't learning anything other than how to excel at George Jetson's job of pressing one button.
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Also when it comes to XI, it's skill ceiling was highly different from XIV. in XI you had something called combat and magic skill, so even if you were power leveled to 50, unless you took the time to lv your combat/magic skill you were pretty much as worthless as half that level if not worse. Powerleveling worked with jobs that shared certain combat skills and allowed the player to bypass the long grind to get x job up but even then XI had another gap in skill that required farming and gil to obtain, magic scrolls. So ya, it's true that if I were to start new as a lv 1 WHM and get PL and only PLed to 99 and nothing else, i'd be far behind because I'd have the magic skill of a lv 1 WHM along with 0 spells to actually play my job.
XIV doesn't have this issue so the aspect of starting at X level doesn't effect the game in the same way it effected XI.