How do you know anyone lied? If you have two fully remote jobs, and the workload for each one is ~20-25 hours a week, and the times don't overlap... I was trying to get you to actually provide reasoning, or evidence, or even "I acknowledge it's my opinion but I feel this way because __________" but here we are with more "I'm right, you're wrong, you're dumb if you disagree."
Please try again because this is a point I'd love to actually discuss rather than just having you talk past me.
Do either of your employers know that (1) you're working for another employer and (2) are actually working 20-25 hours a week when the terms of employment clearly state otherwise (as is almost universally the case with "full-time" employment in the U.S. and just about anywhere else)?
Are you required to tell your employer if you're moonlighting or doing other paid work? I'm not.
Does your employment contract (or the closest thing you have if you work in the US) specify 40 hours a week? Mine doesn't. It says I need to be available during "core hours" which amount to about 17.5 hours a week. It also takes about half a page to basically say "you have to get your assigned work done on time or you may face disciplinary action." If you're available during core hours only, and your stuff gets done, you've fulfilled your end of the bargain.
I've worked placed where you have to have your ass in a seat 42.5 hours a week minus lunch. You can't work there and have another FT job, it's not tenable even for a week or two. But I know a lot of people who either have a FT job and a long-term/large contract position, or two FT W2 jobs simultaneously for months or longer.
Your overly broad "[nearly] universal case" doesn't match the vast majority of the job descriptions I've seen when I was job searching earlier this year. Software development jobs are increasingly remote, and a small subset of those are increasingly asynchronous where they don't care where you are or when you work so long as you get your tasks completed.
Are you required to tell your employer if you're moonlighting or doing other paid work? I'm not.
Actually it's quite common for employment (and even consulting) agreements to have language specifying that you do exactly that -- "devote your full working hours and attention" to their duties for the Company. As well as clauses specifically prohibiting moonlighting (or at least requiring you to declare any such outside relations in writing),
That is: to specifically prevent people from doing what you're doing.
Please try again because this is a point I'd love to actually discuss rather than just having you talk past me.