Regarding league chess I suspect that for ease of administration many local rules will make reference to official laws of chess in some guise or other, and only highlight differences. This may leave grey areas, or differences of practice.
Chess Edinburgh wrote: During a match all players may approach their team captains for advice on points of Law or dispute; but team captains may not give specific advice or contravene the FIDE laws on 'Conduct of the Players'. Players offered a draw, or who wish to offer a draw, may ask team captains for advice provided that the position of the game is neither discussed nor scrutinised by team captains. Team captains shall not offer unsolicited advice to players”;
Meanwhile
Glasgow Chess League wrote: A match captain is not permitted to intervene during play except he/she is authorised to [snip] advise any of his players to make or accept the offer of a draw, but not claim a draw provided he does so in the presence of the opposing match captain.
SNCL rules refer to FIDE rules (which I am unable to locate with a quick search)
Of course, we could argue about things like “intervention”, “points of law”, “advice” or “scrutinised”.
I guess the intention is to allow the captain to represent the team’s interests in decisions over whether to accept (or offer, in some jurisdictions) a draw, but to forbid anything that may be seen as offering advice such as an assessment of a position. This is problematic, as during the normal course of events a captain is likely to have a reasonable idea of what is going on (modulo a recent blunder). An on-the-ball captain may ensure that (s)he is aware of the current position of the relevant boards should the relevant question be asked.
We must also guard against the unscrupulous – where there is communication, there is the chance of coded messages being passed.
The key question to be asked seems to be ”what is needed to get the desired match result?” Sometimes, this is not immediately obvious if there is a handicap or tie-breaking method at play.
I’m not sure that it is explicitly allowed to ask this, although it could be interpreted as it being permissible to ask for advice as this is a question on a point of local law. However, the response may require care. “We need 1.5 points to win” may be an acceptable response. “If you win and Bob draws” could be interpreted as “Bob’s position is level, but I think you are better”.
There is less of a problem if there is only one game to finish – I wouldn’t have a problem with the consequences of win/lose/draw being outlined.
Is casually leaving the results card in a prominent position intervention, or advice, or helpfulness? It happens all the time.
In practice, I cannot recall ever hearing a captain instruct their player to offer a draw.
I have occasionally heard a captain, when asked whether a player could accept a draw, give a rather stilted response along the lines of “the current match score is 3-2 to us” (or whatever), but then captains tend not to know the local rules.
Less often, I have heard a captain respond “up to you” when asked about an early draw offer.
I have seen occasions where people have accepted a draw when they needed to win, because the captain was unable to tell them the match situation.
By far the most frequent occurrence is that players in the last couple of games to be finished will be aware of the match score and of the position on any other boards, and will make up their own minds.
So basically there are slight variations from league to league, it seems to be fairly universal that match scores are communicated, but captain's advice is rarely sought or given - is that a fair summary?