They acknowledged Paul's ministry to the gentiles. They don't have to call him an apostle, but they knew he called himself an apostle and they never disputed it. Peter even closes the chapter by tsaying "which the untaught and unstable distort, as
they do also the rest of the Scriptures, to their own destruction.
17 You therefore, beloved, knowing this beforehand, be on your guard so that you are not carried away by the error of unprincipled men and fall from your own steadfastness"
2 Peter 3:14-17
14 Therefore, beloved, since you look for these things, be diligent to be found by Him in peace, spotless and blameless,
15 and regard the patience of our Lord
as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you,
16 as also in all
his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as
they do also the rest of the Scriptures, to their own destruction.
17 You therefore, beloved, knowing this beforehand, be on your guard so that you are not carried away by the error of unprincipled men and fall from your own steadfastness,
Your really grasping here.