The "others" should provide you a source/citation of where they heard that APKMirror changes dates. As already stated on a previous answer:
Apkmirror.com is run by the same people behind AndroidPolice.com, one of the biggest Android news websites. All uploads are manually vetted and approved, and only free apps are allowed so you won't find any 'cracked' apks or 'warez'.
You might be perplexed by what @bmdixon wrote as there were no citations. To add weight to what he wrote, here are some sample questions and answers from APKMirror FAQ:
What is the connection between APK Mirror and Android Police?
APK Mirror and Android Police are both properties of Illogical Robot LLC, our umbrella company. APK Mirror is managed by the same people who administer Android Police, and the two sites collaborate on an almost daily basis.
Does APKMirror.com host paid or pirated apps?
APKMirror.com has a no-piracy policy and does not host paid apps.
Note: There are very rare exceptions to the no paid apps rule. Sometimes, developers make updates to paid apps available to the public, usually to test beta releases. In such cases, there is usually a license check involved to make sure the apps were previously purchased. MX Player Pro is a notable example of such an exception because J2 Interactive, the app’s developer, provides test APKs on its site.
Security: What measures do you take to make sure all uploaded APKs are real and created by the respective developers?
- All APKMirror.com uploads are verified prior to publishing.
- We make sure that the cryptographic signatures for new versions of all previously published apps match the original ones, which means we know if uploaded APKs were signed by the real devs or someone pretending to be them.
Note: APKMirror.com has been protected from the Janus vulnerability in Android from day one.
- a. For new apps that have never been uploaded to APKMirror.com, we try to match the signatures to other existing apps by the same developer. If there’s a match, it means that the same key was used to sign a previously known legitimate app, therefore validating the new upload.
b. If we see no matches, we try to obtain and compare to a version of the same app from the Play Store or another verified location. If it’s a beta, we will try to get into it. If we can’t, we will attempt to contact the developer.
c. If we’re unable to verify the legitimacy of a new APK, we will simply not publish it.
It's a good policy to always verify if the site and apps are legit even if they come from Play Store. In this case, the people who advise you about APKMirror I think didn't do their own research.