Guardiola has a point if you think there is a contradiction between the rules of the two competitions.
The EFL changed its cup-tied rule with a key restriction linked to the first leg of the semi-finals.
Antoine Semenyo was signed from Bournemouth and Max Alleyne recalled from his loan at Watford before City won 2-0 at Newcastle on 13 January. Both could play for two clubs in the Carabao Cup.
Guehi, though, missed the cut-off by seven days.
The FA, on the other hand, has no cut-off date other than the natural closure of the winter transfer window.
Therefore, even though Guehi featured for Crystal Palace in their FA Cup third round defeat to Macclesfield, he can play for City against Salford in the fourth round on 14 February
And so Guardiola probably has a case that there is no real logic to that arbitrary date in the Carabao Cup.
Also consider that if Guehi had not played for Palace or if he had signed from a European club he would have been able to play for City against Newcastle and Arsenal.
The EFL would argue that the rules were laid out at the start of the season and clubs knew the deadline to sign a cup-tied player.
Even so, the EFL has already tweaked the rules once this season.
The original rule change stated that a player who plays for his parent club and then goes out on loan can play for a second club.
But the wording did not cover a player recalled from loan.
Marc Guiu went on loan from Chelsea to Sunderland and scored for the Black Cats in their 1-1 draw with Huddersfield, a tie they lost on penalties.
After Chelsea suffered injury issues Guiu was brought back to Stamford Bridge before the summer window closed.
Chelsea did not realise the striker was eligible to play for them.
The EFL clarified that for consistency the change should also apply to recalled players.
Guiu then played twice for Chelsea in the competition, against Cardiff and Arsenal.
The EFL says this did not change the fundamental principle of playing for two clubs. The cut-off date of the semi-final has remained consistent.
This article is the latest from BBC Sport’s Ask Me Anything team.