Not personally, but the write ups seem legit for a sim unlocking company.
Suppose the difference has possibly been stated many times over the years, but Sim unlocking is pretty common practice these days. Travel overseas with no roaming costs etc.
Unlike the IMEI unlock from a Apple Cloud, or similar.
[Still only one fix, thats to remove and replace logic boards / chips] many clips on youtube showing this..
Sim is easier, and i'm sure the dodgy crowd this thread was originally based on, uses this to give an air of achieving satisfactory results for some customers.. SIM unlocks only...
The Japanese telco you mention has sold all phones since 2015 with no locks.
I read that they will unlock others for Y 3,000 fee.
They are a big player in the market, with current investments set to expand even more.
I think a sim unlock [from a dedicated network / carrier / retailer is a safe option to try.
And certainly no where near as expensive or risky. [Many you can do yourself, for free]
The IMEI is used to deliver the unlocking, normally with a link up to iTunes for apple devices.
Some can be done free, some after six months, some after contract expires.
(Because of the subsidised phone you may have received in your deal, MRO Monthly Repayment Options.
Built into the plan pricing, and the Telco obviously wants to retain you as long as they can)...