Although oxygen saturation determines the upper size limit for insects,
It is said that insects in the past (except for a few) were not much larger than they are now.
Because the food chain has a bigger impact…
But on English Wikipedia:
https://en.wikipedia.org/wiki/Aphthoroblattina
It says up to 45mm…?
For reference, the largest cockroach fossil from the Carboniferous Period: 9 cm.
https://www.abc.net.au/science/articles/2001/11/08/409585.htm
A Facebook post that openly says ‘It’s not 50cm, it’s 50mm’
https://www.facebook.com/PalaeontologyResearch/photos/apthoroblattina-the-larger-cockroaches-that-lived-in-the-carboniferous-and-permi/341159006078720/
Although it is written in Japanese, it is also stated here that the 50mm is an error.
https://silver-dream.info/2022/07/18/gの原型〜プロトファスマとアプソロブラッティナ/
It’s being spread under the title ‘DNA structure revealed’.
I think it would be better to just see it as a happening.