A very recent BBC article substantiates the hostility to immigration in Japan, and is an interesting read overall:
https://www.bbc.com/news/world-asia-63830490
This is literally the article being rebutted…
I've heard the driver's license test in Japan is quite hard and fails people on the first try just to teach them humility. Maybe they were thinking of that? (whether or not it's true…)
Can a country revoke one’s citizenship as easily as it can revoke one’s permanent residency?
Depends on the circumstances. If it would render you stateless, no (at least for signatories to the relevant convention). Otherwise, it's up to the country; Japan revokes permanent residence (but not citizenship) for those who have left the country permanently (after many years) or those who commit serious crimes, so that's a genuine difference (OTOH citizens can be subject to the death penalty, which I guess amounts to revocation of citizenship in a way). However if you acquired another citizenship, or failed to renounce your previous citizenships when naturalizing, then your citizenship can be revoked as a simple administrative procedure.
Did they substantiate this claim at all? All available public information is that the vast majority of those who try succeed.
People largely don't apply for citizenship, in part because Japan requires them to renounce other citizenships to do so, and in part because a permanent resident can do almost anything that a citizen can in practice.