Manager Gareth Southgate addressed the rest of the group upon their arrival to stress the responsibilities of representing their country and Calvert-Lewin said: "There have been a few lapses in concentration and that's all I would put it down to.
"We're human beings at the end of the day, still learning, still growing. Everybody is likely to make mistakes at certain times but its important you learn from it, you apologise, recognise where you've gone wrong which the lads have done. There's not that feeling [of indiscipline], no.
"It's a difficult time. The boys have apologised and that's first and foremost what they needed to do but we all understand what it means to play for the country and you have to remember that at all times.
"We had a welcome meeting [on Monday] and [Southgate] just reminded us what it means and the expectations of playing for England and you have to be extra, extra careful and follow the rules.
"It's a unique moment in time and we always have to be extra attentive to those rules, and that's the way it is when you're representing your country."
The entire squad were tested on Tuesday, 48 hours before the Wales game in line with UEFA protocols, but Sancho, Abraham and Chilwell were not invited back to take those compulsory tests and will therefore miss the match.
A final decision on whether they will be re-admitted for subsequent UEFA Nations League games against Belgium and Denmark -- assuming they all test negative -- is yet to be taken.
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The controversy follows on from last month's issues when Phil Foden and Mason Greenwood were sent home in disgrace after leaving the bubble in the team hotel in Reykjavik to meet two women just hours after making their debuts against Iceland.
Calvert-Lewin, meanwhile, has made a superb start to the season, scoring nine goals in six games across all competitions -- including two hat-tricks -- to put him at the top of the Premier League goalscoring chart alongside Tottenham Hotspur playmaker Heung-Min Son.
Everton boss Carlo Ancelotti compared Calvert-Lewin to legendary Italy striker Filippo Inzaghi, which inspired him to seek out online videos of the man who netted 156 goals in 370 Serie A games, primarily for AC Milan, in addition to 25 goals in 57 international matches.
"Funnily enough, he mentioned it to me before he came out and said it in the press," said Calvert-Lewin. "I had a little YouTube of his goals and I watched a 15-minute reel of him. A lot of his goals are one-touch finishes and he has got great movement.
"You can always learn off him, I am still learning now. I am learning my craft. [Carlo] has had a positive influence on me. At the age I am getting to now, I am evolving and learning my craft.
"I am fine-tuning certain aspects of my game. Beforehand, I was guilty of doing a lot of my best work away from the goal. But now I am getting in between the sticks and putting the ball in the back of the net.
"That analogy from Carlo was more of an emphasis on being in the right place at the right time, not to say I am a carbon copy of Pippo Inzaghi but there are elements of his game that I have been showing in my game and they are one-touch finishes and being in the right areas to put the ball in the back of the net."
