It is intolerable for the judicial system to treat people this way, and there is not even a technical justification for condoning this bait and switch.
What was at stake? The man was convicted of murder and serving a sentence of 15 years to life. This was an appeal of his denial of relief in a collateral attack on his sentence in federal court.
The man was represented by an attorney whose assistance on the habeas appeal was obviously ineffective in hindsight, and was denied appellate review only because his attorney, through no fault of the individual serving the sentence, relied on an court order regarding the deadline. Four out of nine justices on the U.S. Supreme Court thought his attorney did the right thing and was a good lawyer. But, you do not have a constitutional right to effective assistance of counsel for habeas corpus petitions, as you do on a direct appeal if one is available, so the man in prison can't file a new petition claiming ineffective assistance of counsel in his habeas corpus petition.
The real game being played in this case is that conservatives simply do not like federal habeas corpus petitions and are looking for any grounds to deny them, because the conservative majority feels that these petitions are almost per se frivilous. Basically, conservatives think that direct appeals are enough due process, and liberals question that assumption.
Most of the time the conservatives are right. Something like 98% of federal habeas corpus petitions do not prevail. But, the exceptions (including something like 40% of death penalty cases where defendants usually are represented by counsel), are important ones in the eyes of liberals.