Some native speakers say this "war journalist" made many odd spelling errors. They also don't know who he is and suspect he's fake. I imagine Ukraine is sowing confusion and also shelling and probing in many other areas along the entire front to keep Russia guessing. But I take these random reports of retaking multiple large towns simultaneously with a huge grain of salt.
This
Radio Free Europe/Radio Liberty article has some good info, including a video with clips of a local Ukrainian commander. Regional officials say
Kupyansk is liberated and show a pic of four soldiers with flags in front of
this Kupyansk gov't building. It's a bit north of the city center on the west side of the Oskil River. Ukraine officially released a pic of a special ops group in Kupyansk, but they were clearly on the outskirts. There are also reports the bridge is damaged. The lack of fighting on the west half of town makes me suspect Russia retreated across the river to the eastern half and blew the bridge. That makes sense for an army being overrun. If they abandoned the eastern half of the city as well then I don't know what to think. That side is a logistics hub supplying the entire region. The river makes it much easier to defend. It makes no sense at all to just walk away.
On the other hand, I can definitely see Russia abandoning Izium and setting up on the other side of the Oskil River. Izium has no real strategic value and they can connect from the Oskil dam down to the Siverskyi-Donets River. That would explain why they're actually fighting in Lyman and Svyatohirsk and not in Izium.
It's a fluid situation, though. Russian propagandists also seem confused.