I am not being flippant. Rather I was thinking of this review study of "lactose
intolerance" that I've read recently (couple of days ago):

Allaying Fears and Fallacies about Lactose Intolerance

https://www.sciencedirect.com/science/article/abs/pii/S00028...

Abstract

Public awareness and misunderstandings of lactose intolerance are at an
all-time high. Many people erroneously believe they are lactose intolerant or
develop gastrointestinal symptoms after intake of lactose. Consequently,
lactose-containing foods such as milk and other dairy foods may be eliminated
unnecessarily from the diet. Because these foods are a major source of
calcium, low intake of them can compromise calcium nutriture. This, in turn,
can increase the risk of major chronic diseases such as osteoporosis (porous
bones) and hypertension. This review is intended to help dietetics
professionals alleviate clients' fears about lactose intolerance and recommend
dietary strategies to improve tolerance to lactose. Scientific findings
indicate that the prevalence of lactose intolerance is grossly overestimated.
Other physiologic and psychologic factors can contribute to gastrointestinal
symptoms that mimic lactose intolerance. Scientific findings also indicate
that people with laboratory-confirmed low levels of the enzyme lactase can
consume 1 serving of milk with a meal or 2 servings of milk per day in divided
doses at breakfast and dinner without experiencing symptoms. Several dietary
strategies are available to help lactose maldigesters include milk and other
dairy foods in their diet without experiencing symptoms.

The full study cites results from breath hydrogen tests to support its claim
that "the prevalence of lactose intolerance is grossly overestimated" (as
stated in the abstract, above). In particular:

A diagnose of lactose maldigestion [by an increase in breath hydrogen
concentration of 20 ppm or more above the baseline value measured by a breath
hydrogen test] does not predict the occurrence of symptoms of intolerance (12,
13, 15, 22, 28, 30). Nor can symptoms that follow lactose or milk intake be
used to diagnose low lactase levels or lactose maldigestion (28). Intolerance
symptoms after a lactose load have been demonstrated to occur in lactose
maldigesters and lactose digesters (28).

Or, in other words (citing from the paper):

There is no clear correlation between lactose maldigestion, lactose
intolerance, and milk intolerance. This may be explained by the subjectiveness
of symptoms and the quantity of lactose or milk required to demonstrate
symptoms. Strong beliefs may contribute to lactose intolerance; that is,
persons who believe they are lactose intolerant may experience symptoms
(12,30). Johnson et al (12) reported that when 45 lactase-deficient
African-Americans were fed either a lactose-containing milk or
lactose-hydrolyzed milk under boudle-blind conditions, on third of the
subjects experienced some minor intolerance to both types of milk. The
subjects' symptoms were not due to the lactose content of milk, but perhaps to
social and cultural attitudes that influenced their ability to tolerate milk
(12). In a more recent double-blind investigation, Vesa et al (3) found that
one half of lactose maldigesters reported symptoms after consuming a
lactose-free milk or a greater level of symptoms after intake of smaller
rather than larger intakes of lactose. The symptomes were due, therefore, to
factors other than lactose intake.

I note that this is one study and rather dated, but I just happened to
stumble upon it while looking for something else. There may be newer studies
in the literature that contradict this one's findings.

Edit: also, I used the term "gluten intolerance", not "coeliac disease".
Please don't accuse me of being flippant about coeliac disease when I did no
such thing.