That's the logical answer.
But FT isn't dictated by logic. The powerups that the relevant characters get are weird AF. Espeically, our 20-25 year old characters just flying past highly experienced mages in power level, with 1-2 year trainings.
Three main examples of retarded power scaling:
1. x784 Gildarts in around 40 years old. And he's around Jura level, according to Makarov. Stronger surely, but he would have about the same difficulty or more difficulty as he had defeating Bluenote, for Jura.
At best, he was GOI 4 (Warrod) tier. But, in just one year, this wandering mage that barely trains anymore, jumped up tiers to reach on or above God Serena tier. Does this make any sense? He jumped up tiers that he didn't in 40 years of his lifetime.
2. x784 Jellal was around x784 Laxus level. And was above x784 Jura with his illusion (higher ranking WS).
In 6 years (1 year in prison) timeskip, and with 2nd origin (presumably); he reached only around x791 Jura level? This means that he got a LESSER powerup than what Jura himself got. WTF ?? And Laxus trained for just 3 months to have same powerup Jellal got in 6 years and with 2nd origin?
To make matters worse, Jellal jumped up tiers in 1 year to reach high Spriggan tier, while Jura remained stagnant (at least as far as we know).
Yeaaa, very logical there, Mashima
3. Mira stopped using magic and became a bartender 3 years prior to the start of main series. While Erza trained. And in x784, even after Mira potentially got weaker or at the very least stagnant (because of not using magic for 3 years), she was still somewhere close to Erza in her Satan Soul (at least mid diff range). And, that was her without using her Sitri and Halphas.
Point being: Mashmia just makes our characters as strong as he wants them to be, irrespective of any logic or respect to the verse.