I have to say as a counter point though that I've had a lot more trouble with coworkers coming to my physical desk for questions that they could have Googled than with Junior getting stuck for extended period of time remotely. It's all a matter of culture and relationships.
Oh come on... I get arguing that there are ways to make remote training good enough. Maybe even similar. Maybe even a net-positive when you look at the entire picture (including the productivity and happiness of your senior staff). But saying remote is better for training specifically? No way. That makes no logical sense.
In person: Usually have to face the person or the screen, can't see both. I have to write down commands and pass them, or type them myself. There is a delay finding others if we need to talk to them. More chance to transpose commands incorrectly by the user. Harder to record the session without losing parts.
So at minimum, in person would be the same. So I can't possibly see how in person could be worse.
In person is worse. I've done both. It's noisier, you're crammed into a cube taking notes, etc. If you're going to use remote tools, what's the benefit of in person?
Got it, I see you're in the "make up stuff about the other person" phase of the discussion. No point in continuing here.
They won't do that every single time. At some point they'll realize that asking for help isn't an issue.
Part of learning to be a sw developer is learning how to go about your work. Learning when to ask for help. If someone is doing this for you, you'll never going to learn.
Part of being a senior engineer is to use the mentorship skills you developed along the way and make judgements about how much struggle is right. Every new person should have a more senior partner with whom they can ask the dumb questions and not be made to feel dumb.
There are whole college degree programs designed to teach this, in fact.
It's clear which juniors are motivated and will make the most of the mentorship and which ones are not. Some are just there for the check and you cannot compromise your senior and higher talent on people who don't want to learn and grow and just want the prestige and check of a high-tech job. It's the same situation with someone who is drowning not listening to orders and taking down their rescuer with them too.
If a junior needs someone to sit next to them because they toil for way longer than needed on clear simple requirements and goals, this may not be the field for them. I never needed anyone right next to me that couldn't have been a direct message or a brief remote call to clarify something specific, clear, and to the point. You're describing a reality where the people who don't do are just trying to take as much time for themselves as possible to hide the fact that they don't want to think.
And very importantly, I'm saying 30-60 minute remote check-ins are an absolutely insane idea that should never be implemented.
I don't know any kind of remote system that provides for anything even close to the power of in-person mentoring.
How about letting them figure it out and provide opportunities to chat and ask questions from time to time. Everyone wants superdevelopers but everyone expects that you're going to put a complete noob in a room with a senior developer, they're gonna rub hand and in 2-4 days you're going to have another senior developer. That's not how it works.
We've used day long zoom windows or slack huddles. Keep muted until you want to say something. Slack is the same thing, just send a message.
But... how? Remote check-ins with juniors every 30-60 minutes? That's crazy. But that's basically the only way to replicate the in person experience.
The best mentoring results for me as the mentee and for me as a mentor have been when we're sitting next to each other. The mentor can visually tell when the mentee is stuck, and mentee can tell when the mentor isn't focusing on anything important and is more willing to ask for help.
No matter how many times you tell junior engineers to ping you at the first sign of trouble, they're not going to do it. They're going to toil for way longer than needed, unless you're sitting right next to each other.